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71.
Junhyong Kim Mark A. Burgman 《Evolution; international journal of organic evolution》1988,42(3):596-602
A comparative study of the accuracy of three different approaches to phylogenetic estimation was made on simulated data with differing rates of change in different lineages. The three approaches were maximum likelihood, maximum parsimony, and phenetic clustering. The data were generated by simulating genetic drift with different population sizes over a simple four-species tree topology. Although the accuracy of all three approaches was found to be dependent on the number of loci (characters), maximum likelihood was found to perform considerably and consistently better than maximum parsimony or phenetic clustering. 相似文献
72.
Consumption of leaf detritus by a stream shredder: Influence of tree species and nutrient status 总被引:8,自引:3,他引:5
Four species of riparian vegetation (alder, birch, willow and poplar) were fertilized with nitrogen, phosphorus, nitrogen
+ phosphorus, or no fertilizer (control). The resulting leaf detritus (leached but not microbially colonized) was offered
to a stream shredder, Hydatophylax variabilis (Trichoptera: Limnephilidae). In one experiment, shredder consumption of leaf detritus from different nutrient treatments
(within tree species) was compared, and in a second experiment, consumption of different tree species (within nutrient treatments)
was compared. Larvae preferred leaf detritus from nitrogen + phosphorus treatments (except in poplar where nitrogen treatment
was preferred). Alder was preferred over other tree species for all treatments. Chemical and physical analyses of leaf litter
showed differences between tree species and nutrient treatments in nutrient content, tannins and leaf toughness. Leaf consumption
by larvae was positively associated with nitrogen content and negatively associated with condensed tannin content. Species
composition and nutrient status of riparian vegetation may strongly influence detrital food webs in streams. 相似文献
73.
Mark Tony Lieberman Robert M. Zablotowicz Naida P. Davis-Omholt 《Applied microbiology》1986,51(4):715-719
An improved method for antibiotic resistance recovery of Bradyrhizobium japonicum from soybean (Glycine max (L.) Merr.) nodules that is simple, time saving, and economical was developed. This technique involves the use of two 96-well microtiter plates as a multinodule sterilization chamber and a template and a third plate as a 16-point replicator constructed with steel nails affixed to the plate with epoxy cement. With this system a team of four technicians could type 3,000 nodules per day. This method was useful in assessing strain establishment and interstrain competition when one or more uniquely labeled strains of B. japonicum were inoculated onto either growth-room- or field-grown soybeans. Contamination was low and reproducibility across replicates approached the theoretical upper limit. Simplicity in design and use made this recovery method especially adaptable for field studies in which large numbers of nodules were required to provide a representative statistical sample offering good precision. 相似文献
74.
The decolorization of the polymeric dye Poly-Blue (polyvinalamine sulfonate-anthroquinone) by lignin degrading fungi 总被引:2,自引:0,他引:2
Summary In this work we have investigated the decolorization of the polymeric dye Poly-B411 by several fungi. Only fungi with known lignin degrading ability were able to decolorize the dye. Pleurotus ostreatus sp. florida decolorized the dye both in solid and liquid media. Decolorizing ability developed in the absence of the dye but only when the fungus had been previously cultivated on lignin containing substrates.The work was supported by a grant from the Charles Wolfson Trust 相似文献
75.
Mark S. Graham Garth L. Fletcher 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(4):455-459
Summary The viscosities of blood from shorthorn sculpin (Myoxocephalus scorpius), longhorn sculpin (Myoxocephalus octodecemspinosus) and winter flounder (Pseudopleuronectes americanus) were compared using a cone-plate viscometer. Both species of sculpin were almost identical with respect to blood and plasma viscosity at the temperatures (0 and 15°C) and shear rates (2.3–90/s) examined. In contrast, the viscosities of winter flounder blood and plasma were considerably greater than those observed in the sculpins. This difference in blood viscosity between the shorthorn sculpin and the winter flounder persisted over the hematocrit range of 0 to 40% red blood cells. The viscosity of the plasma and the interactions between plasma proteins and red blood cells appeared to be the major reasons for the relatively high viscosity of the flounder blood. Although a proportion of the flounder blood viscosity was attributable to fibrinogen, other plasma proteins also appeared to play a significant role. The relatively low blood viscosity of the sculpin species may confer a circulatory advantage during periods of low water temperatures. 相似文献
76.
Thiols and pancreatic beta-cell function: a review 总被引:2,自引:0,他引:2
In pancreatic islets insulin secretion in response to a variety of stimulators is sensitive to the redox state of extracellular and intracellular thiols. In this connection variations of plasma glutathione (GSH) may also be of importance. In the process of stimulus-secretion coupling, membrane thiols play an important role. One major localization of critical thiols appears to be related to the influx of calcium through the voltage-dependent channel. Other transmembranal ion movements and the cAMP system seem to be less sensitive to thiol oxidation than calcium influx via voltage-dependent Ca channels. 相似文献
77.
A new algorithm is described that will rapidly produce restrictionmaps of cloned DNA fragments. Information concerning the vectoris stored as a data file and used in constructing probable maps.As the program is based upon a permutation analysis it has twoprimary uses. First, preliminary restriction maps can be createdfrom fragment length data as a starting point for further analysis.Second, existing maps can be confirmed as being highly probable,and other probable maps examined to ensure certain combinationshave not been overlooked. Although primarily designed for linearvectors, the program can be used to calculate circular maps.
Received on June 5, 1985; accepted on September 27, 1985 相似文献
78.
Mark M. Littler Diane S. Littler 《Journal of experimental marine biology and ecology》1984,74(1):13-34
The general hypothesis that morphological, physiological, and ecological adaptations of macro algal functional-form groups can be related to the level of disturbance encountered in a natural environment was examined. Two articulated calcareous coralline algae (Amphiroa van-bosseae Lemoine, 24% cover and Corallina frondescens Post. & Rupr. 20%) and one non-articulated coralline alga (Lithophyllum sp., 16%), all late-successional predation-tolerant strategists, comprise most of the community cover on stable bedrock substrata at Punta Las Cuevitas, Sonora, Mexico. Conversely, Ulva rigida C. ag. (26% cover) and a ralfsioid crust (23%), shows to be early-successional opportunistic strategists, cover more of the disturbed boulder habitat. Porolithon sonorense Daws., a stress-tolerant strategist, is uniquely abundant on both substratum types (13% cover on boulders, 10% on bedrock). The sheet-like and filamentous algae, prevalent in the temporally unstable habitat, generally show greater productivity (>2×) than the thicker and calcareous forms conspicuous in the more constant environment. It appears that selection for delicate thalli with high productivities, as well as selection for tougher morphologies having lower photosynthetic rates due to greater proportions of structural tissues, are widespread, divergent evolutionary forces among marine algae. Experiments with captive sea urchins (Echinometra vanbrunti Agassiz), in conjunction with fish-preference data published for some of the same algae studied here, offer strong support for the functional-form model. Parrotfishes, rudderfishes, surgeonfishes, damselfishes and E. vanbrunti, in the Gulf of California, preferentially feed on delicate, early-successional, sheet-like, and filamentous algae, while rejecting or ignoring the more structured, late-successional and calcareous algae. There is no significant (P > 0.05) gradation in calorific content between the first four of the six functional groups (i.e., Sheet-, Filamentous-, Coarsely Branched- and Thick Leathery-Groups), but the mean value for these fleshy forms (2.6 kcal · g ash-free dry wt?1) is significantly greater than that for the last two groups (0.3 kcal, Jointed Calcareous- and Crustose-Groups). The approach used in this study demonstrates a realistic technique for predicting macrophyte community composition from knowledge of the disturbance levels in a given habitat or the reverse. The form group-disturbance relationship has important implications for future biological monitoring of rocky-inter-tidal and subtidal systems. 相似文献
79.
The amino acid sequences of cytochrome c553 from the eukaryotic red alga Porphyridium cruentum and from the prokaryotic cyanobacterium Aphanizomenon flos-aquae have been determined from the tryptic and cyanogen bromide peptides. The results indicate that a charged region of these proteins has evolved with special rapidity to accomodate a rapid evolution of a binding site in the P700 electron acceptor complex. 相似文献
80.
Mark Sullivan 《Culture, medicine and psychiatry》1986,10(4):331-350
Medicine's inability to humanely respond to the concerns of its patients has often been attributed to its Cartesian dualism of mind and body. More recently, this inability has been ascribed to medicine's penchant for isolating biological disease as its sole proper concern to the exclusion of experienced illness. This dualism of disease and illness is claimed to be an outgrowth of the Cartesian dualism but the differences and similiarities between these two forms of dualism is not clear. This paper seeks to clarify their relationship through an examination of their historical origins.Disease is currently identified and characterized by a process of clinico-pathological correlation. By this means clinical impressions are corrected in light of autopsy findings. Our current mode of clinico-pathological correlation originated in Paris in the early nineteenth century with the work of Xavier Bichat and others. The theory of knowledge implicit within this clinico-pathological approach to the body is described and compared to that of Descartes. Though medicine does pursue certain Cartesian goals for knowledge, such as knowledge of the patient that does not rely upon his candor, it ultimately espouses neither a Cartesian theory of knowledge nor a Cartesian theory of the body. With pathological inquiry modeled after the autopsy as the final word in the identification and characterization of disease, the patient's capacity for self-knowledge and interpretation — not an entity called mind — is isolated away from his body. This approach to the body means that objective evidence of disease is valued to the exclusion of subjective evidence.If the shortcomings of modern biomedicine are to be effectively addressed, not only must the interdependence of disease and illness be acknowledged. The very canons of medical evidence must be revised. Subjective evidence must be rehabilitated and rejuvenated with better methods of subjective clinical investigation. Host factors relevant to the healing and knowing of sickness must be elucidated so that medicine may rediscover the sentience of its patients. Department of Psychiatry and Behavioral Sciences University of Washington Seattle, WA 98195, U.S.A. 相似文献