Removal of blood group determinants from bovine erythrocyte membranes. 3. Action of proteolytic enzymes on intact cells

Bovine erythrocyte treatment with chymotrypsin, trypsin, pronase, papain, or ficin eliminated or weakened the reactivity of 18 of the 47 blood group factors which were examined. Thirteen of the affected factors were from the B system, and one each was from the C, FV, L, M, and R'S' systems. Variation attributable to pheno-group (allele) or genotype influences was observed in the effects upon six of the factors. Ficin-treated V/V, but not F/V or F/F, cells were rapidly lysed by normal rabbit serum (complement control). Absorptions with pronase-treated V positive cells indicated that essentially all V antigenicity was removed. However, immunizations with pronase-treated V positive cells elicited V antibody production in one of two recipient cows. The numbers of antigens removed by different enzymes did not appear to be closely related to the amount of protein removed.     

Global reorganization of budding yeast chromosome conformation in different physiological conditions

The organization of the genome is nonrandom and important for correct function. Specifically, the nuclear envelope plays a critical role in gene regulation. It generally constitutes a repressive environment, but several genes, including the GAL locus in budding yeast, are recruited to the nuclear periphery on activation. Here, we combine imaging and computational modeling to ask how the association of a single gene locus with the nuclear envelope influences the surrounding chromosome architecture. Systematic analysis of an entire yeast chromosome establishes that peripheral recruitment of the GAL locus is part of a large-scale rearrangement that shifts many chromosomal regions closer to the nuclear envelope. This process is likely caused by the presence of several independent anchoring points. To identify novel factors required for peripheral anchoring, we performed a genome-wide screen and demonstrated that the histone acetyltransferase SAGA and the activity of histone deacetylases are needed for this extensive gene recruitment to the nuclear periphery.     

The freezing and preservation of bovine erythrocytes in liquid nitrogen

Bovine erythrocytes can be preserved for long periods of time by freezing and storing in liquid nitrogen. Blood group determinations, titrations, and isoimmunizations indicated that there were no detectable alterations in antigenic reactivities of preserved erythrocytes when compared with fresh samples of blood from the same animal. In addition, consistent percentages of recovery within a frozen mixture could be obtained, indicating that the deterioration of erythrocytes with time was not significant. Variations in the percentage of recovery of erythrocytes with different concentrations of sucrose (the cryoprotective agent) were significant at the 0.01 level of probability. The highest average percentages of recovery of erythrocytes from whole blood and the cellular fraction of blood (blood from which plasma was removed before freezing) were obtained with 45 and 40% sucrose, respectively. Results also indicated that whole blood gave a slightly higher percentage of recovery, than the cellular fraction. The individual donor effect, storage time in liquid nitrogen, and various saline concentrations of the thawing and washing solutions had no significant effects upon percentage of recovery.     

Traits and growth of liana regeneration in primary and secondary forests of Central Amazonia

Question: Do traits of liana regeneration differ among secondary forest types of varying land‐use history and primary forest? Location: Eighty kilometers north of Manaus, Brazil. Methods: We compared plant functional traits and growth rates of liana regeneration (<1.7‐m length) among two secondary forest types and primary forest. Secondary forest types were: Vismia (on land formerly clear‐cut, used for pasture and intensively burned) and Cecropia (no pasture usage or intensive fires after clear‐cut). Results: A principal components analysis indicated that most of the primary forest species exhibited a similar habit and were characterized by short shoots and small, round leaves with low specific leaf area, whereas secondary forest species had a broad range of trait values. At the plot level, primary and secondary forest communities were separated mainly by plant length and leaf size. Plant size varied more within secondary than within primary forest plots. The two secondary forest types could not be separated based on the traits of liana regeneration. Relative growth rate (RGR) did not correlate significantly with any measured plant trait, except for a negative relation to initial length. RGR increased with decreasing canopy cover and was highest in Vismia forest plots. Conclusion: Plant functional traits of liana regeneration were more similar in the primary forest and differed substantially from secondary forests, yet canopy cover only partly explained the observed differences.     

A multilocus study of pine grosbeak phylogeography supports the pattern of greater intercontinental divergence in Holarctic boreal forest birds than in birds inhabiting other high-latitude habitats

Aim Boreal forest bird species appear to be divided into lineages endemic to each northern continent, in contrast to Holarctic species living in open habitats. For example, the three-toed woodpecker (Picoides tridactylus) and the winter wren (Troglodytes troglodytes) have divergent Nearctic and Palaearctic mitochondrial DNA clades. Furthermore, in these species, the next closest relative of the Nearctic/Palaearctic sister lineages is the Nearctic clade, suggesting that the Palaearctic may have been colonized from the Nearctic. The aim of this study is to test this pattern of intercontinental divergence and colonization in another Holarctic boreal forest resident – the pine grosbeak (Pinicola enucleator). Location The Holarctic. Methods We sequenced the mitochondrial ND2 gene and Z-specific intron 9 of the ACO1 gene for 74 pine grosbeaks collected across the Holarctic. The sequences were used to reconstruct the phylogeographical history of this species using maximum likelihood analysis. Results We discovered two distinct mitochondrial and Z-specific lineages in the Nearctic and one in the Palaearctic. The two Nearctic mtDNA lineages, one in the northern boreal forest and one in south-western mountain forest, were more closely related to each other than either was to the Palaearctic clade. Two Nearctic Z-chromosome clades were sympatric in the boreal and south-western mountain forests. Unlike the topology of the mtDNA tree, the relationship among the Z-chromosome clades was the same as in the three-toed woodpecker and winter wren [Nearctic (Nearctic, Palaearctic)]. The Palaearctic Z-chromosome clade had much lower genetic diversity and a single-peak mismatch distribution with a mean < 25% of that for either Nearctic region, both of which had ragged mismatch distributions. Main conclusions Our data suggest that, similar to the other boreal forest species, the pine grosbeak has divergent lineages in each northern continent and could have colonized the Palaearctic from the Nearctic. Compared with many Holarctic birds inhabiting open habitats, boreal forest species appear to be more differentiated, possibly because the boreal forests of the Nearctic and Palaearctic have been isolated since the Pliocene (3.5 Ma).