Isolation of selective 3H-chlornaltrexamine-bound complexes,possible opioid receptor components in brains of mice

The nonequilibrium narcotic antagonist, chlornaltrexamine (CNA) was used to bind selectively and covalently pioid specific sites on brain membrane preparations. Selective binding of [³H]CNA occured with a saturation maximum of 185 fmol/mg protein. Bound [³H]CNA was extracted with Triton X-100, dialyzed against Brij 36T, precipitated with trichloroacetic acid and chromatographed on an ultrogel AcA 22 column. The elution profile suggests that this extract contains a minimum of four selective [³H]CNA complexes. At least two of these complexes migrate in a single large peak. Column calibration showed that this peak eluted at 590,000 daltons. One of these specific [³H]CNA complexes elutes at the elution volume of the column and is dialyzable. Finally, putative aggregate of these complexes elutes with the void volume.     

DEVELOPMENT AND ORGANIZATION OF THE SECONDARY VESSEL SYSTEM IN POPULUS GRANDIDENTATA

The apical 22 cm of a dormant, first-year sprout of Populus grandidentata was sectioned serially, and the primary and secondary xylem systems were studied microscopically and graphically reconstructed. A total of 15 nodes was present on the mature stem and 14 foliar primordia in the dormant bud. The vascular traces in the lower portion of the mature stem conformed to a 2/5 phyllotaxy while those of the upper portion and within the dormant bud conformed to a 3/8 phyllotaxy. The 2/5 to 3/8 phyllotactic transition occurred in an extremely precise and systematic two-step pattern: (1) The lateral traces shifted to a new point of origin on the parent central trace, and (2) three new central traces were initiated in sequence by divergences from left-traces. Metaxylem, when followed downward, conformed to the arrangement of the procambial trace system only within one orthostichy. Below this point, the metaxylem components of lateral traces physically separated from those of the protoxylem and continued downward on a new course. Metaxylem vessels produced by the trace cambium originated from a postulated vessel-generating center at the stem-petiole junction. Each metaxylem vessel developing basipetally through the primary body was continuous with a secondary vessel developing basipetally in the secondary body. Because secondary development closed the vascular cylinder, vessels originating from developing leaves or primordia situated at higher levels in the shoot were displaced radially outward when they entered the secondary xyelm. The distribution of vessels in the secondary xylem can therefore be accounted for by a knowledge of the production and distribution of metaxylem vessels in the primary body.     

Purification, characterization, and quantitation of the antigen employed in the immunodiffusion test for diagnosis of equine infectious anemia.

Equine infectious anemia (EIA) antigen extracted from the spleen of horses infected with EIA virus was purified by pH treatment, (NH4)2SO4 fractionation and affinity chromatography. The homogeneity of the antigen was indicated by sedimentation rate and sedimentation equilibrium experiments. A S20,w of 0.51 was determined and a molecular weight of 7600 was calculated from sedimentation equilibrium analysis. The amino acid composition of the pure antigen indicated the antigen is an acidic protein. Employing radical immunodiffusion (RID) and pure antigen a method for quantitating antigen content of antigen containing preparations was developed.     

Does juvenile competition explain displacement of a native crayfish by an introduced crayfish?

The coldwater crayfish Orconectes eupunctus is endemic to the Spring and Eleven Point Rivers of Arkansas and Missouri, and appears to have been displaced from a portion of its range by the recently introduced ringed crayfish Orconectes neglectus. We examined competition among juveniles as a potential mechanism for this crayfish species displacement through laboratory and field experiments. Orconectes eupunctus juveniles survived and grew in stream cages in their former range, implicating biotic interactions rather than habitat degradation in the displacement. Laboratory experiments revealed O. neglectus juveniles were dominant in the presence of limited food, whereas size rather than species determined occupancy of limited shelter. In a field competition experiment using stream cages, O. neglectus juveniles did not inhibit growth or reduce survival of O. eupunctus juveniles. Consequently, laboratory evidence of O. neglectus dominance did not correspond with competition under field conditions. Combined with previous studies examining the effects of O. neglectus on O. eupunctus, these results suggest that competition may not be a factor in this crayfish species displacement. Alternate mechanisms for the apparent displacement of O. eupunctus by O. neglectus, such as differential predation or reproductive interference, should be investigated.     

Community structure of epilithic and endolithic algae and cyanobacteria on cliffs of the Niagara Escarpment

Abstract. In order to understand how communities of rock-inhabiting micro-organisms are spatially organized, rock samples and environmental variables were collected from five cliff sites in Ontario, Canada. Algae and cyanobacteria were extracted from the epilithic zone (rock surface) and endolithic zone (subsurface) of 180 samples, and the frequency of each taxon (genus or larger) was determined. Multivariate statistical analyses were used to determine (1) the variation in community composition on different spatial scales; (2) differences in community composition between surface and subsurface; and (3) the environmental constraints of community structure. 13 taxa of cyanobacteria and 12 taxa of eukaryotic algae were identified in the endolithic zone, and 17 and 14 in the epilithic zone, respectively. The most frequent taxa were similar in both zones, but MANOVA of species frequencies showed significant differences between endolithic and epilithic communities. DCA and CCA showed that geographic-scale variation in community composition was the dominant trend in the data for both surface and subsurface. Cyanobacteria and eukaryotic algae showed a clear separation on the first ordination axis. When the geographic-scale variation was removed in a partial ordination, the separation of organisms by kingdoms disappeared and epi- and endolithic ordinations were no longer similar. Light then appeared to control the endolithic species composition, while other factors, possibly moisture-related, were suggested for the epilithic community. Despite biomass and productivity that varies mostly at scales of < 1m², we conclude here that species composition and its environmental constraints vary at small as well as larger scales.     

Correlations between net auxin and secondary xylem development in young Populus deltoides

Stems of cottonwood ( Populs deltoides Bartr. ex Marsh.) plants grown under different conditions were examined to determine the relation between net endogenous auxin yields and the acropetal advance of the primary-secondary vascular transition zone (TZ). In all treatments, the internode yielding maximum net auxin activity, as determined by the Avena curvature bioassay, closely corresponded with the internode in which the TZ occurred. Under short-day (SD) dormancy-inducing conditions, auxin yield declined steadily while the maximum auxin peak and the TZ shifted toward younger internodes. Auxin yields from these plants were extremely low after 5 weeks of SD compared with those from long-day (LD) plants. The only consistent auxin yield was obtained from internodes subtending young leaves beneath the apical bud. Plants placed in SD for 3 weeks and then returned to LD conditions showed an immediate increase in auxin yield in the stem, and the progressive acropetal advance of the TZ under SD was reversed. Therefore, within 7 LD the positions of the TZ and peak auxin yield corresponded to those observed before the imposition of SD Fully dormant plants placed in LD showed a dramatic rise in auxin yields during the first 2 weeks of renewed growth. Although low levels of auxin were found in the newly developing shoots after 6 LD, yields increased rapidly after 9 and 14 LD. The position of the TZ corresponded with the peak of net auxin activity after 9 and 14 LD.     

Attack of the PCR clones: Rates of clonality have little effect on RAD‐seq genotype calls

Interpretation of high‐throughput sequence data requires an understanding of how decisions made during bioinformatic data processing can influence results. One source of bias that is often cited is PCR clones (or PCR duplicates). PCR clones are common in restriction site‐associated sequencing (RAD‐seq) data sets, which are increasingly being used for molecular ecology. To determine the influence PCR clones and the bioinformatic handling of clones have on genotyping, we evaluate four RAD‐seq data sets. Data sets were compared before and after clones were removed to estimate the number of clones present in RAD‐seq data, quantify how often the presence of clones in a data set causes genotype calls to change compared to when clones were removed, investigate the mechanisms that lead to genotype call changes and test whether clones bias heterozygosity estimates. Our RAD‐seq data sets contained 30%–60% PCR clones, but 95% of RAD‐tags had five or fewer clones. Relatively few genotypes changed once clones were removed (5%–10%), and the vast majority of these changes (98%) were associated with genotypes switching from a called to no‐call state or vice versa. PCR clones had a larger influence on genotype calls in individuals with low read depth but appeared to influence genotype calls at all loci similarly. Removal of PCR clones reduced the number of called genotypes by 2% but had almost no influence on estimates of heterozygosity. As such, while steps should be taken to limit PCR clones during library preparation, PCR clones are likely not a substantial source of bias for most RAD‐seq studies.