The late-replicating X chromosome in digynous mouse triploid embryos

Using BrdU-labeling and acridine orange staining, the behavior of X-chromosome replication was studied in 28 XXX and 19 XXY digynous mouse triploids. In some of these the paternal and maternal X chromosome could by cytologically distinguished. Such embryos were obtained by mating chromosomally normal females with males carrying Cattanach's X chromosome which contains an autosomal insertion that substantially increases the length of this chromosome. In the XXX triploids there were two distinct cell lines, one with two late-replicating X chromosomes, and the other with only one late-replicating X. The XXY triploids were also composed of two cell populations, one with a single late-replicating X and the other with no late replicating X chromosome. Assuming that the late-replicating X is genetically inactive, in both XXX and XXY triploids, cells from the embryonic region tended to have only one active X chromosome, whereas those from the extra-embryonic membranes tended to have two active X chromosomes. The single active X chromosome was either paternal or maternal in origin, but two active X chromosomes were overwhelmingly maternal in origin, suggesting paternal X-inactivation in extra-embryonic tissues.     

Redistribution of Tritium during Germination of Grain Harvested from myo-[2-H]Inositol- and scyllo-[R-H]Inositol-Labeled Wheat

Wheat kernels from myo-[2-³H]inositol- or scyllo-[R-³H]inositol-labeled plants (Sasaki and Loewus 1980 Plant Physiol 66: 740-745) were used to study redistribution of ³H into growing regions during germination. Most of the labeled 1-α-galactinol (or the analogous scyllo-inositol galactoside) was hydrolyzed within 1 day. Water-soluble phytate was dephosphorylated within 3 days. A large reserve of bound phytate continued to release myo-inositol over several days. Translocation of free myo-inositol to growing regions provided substrate for the myo-inositol oxidation pathway and incorporation of ³H into new cell wall polysaccharides.     

Topographic examination of sister chromatid differential staining by nomarski interference microscopy and scanning electron microscopy

BrdU-substituted Chinese hamster chromosomes were treated with a hot Na₂HPO₄ solution and stained with Giemsa to produce sister chromatid differential staining (SCD). The process of SCD was examined with the Nomarski differential interference microscope and the scanning electron microscope. After the Na₂HPO₄ treatment alone, unifilarly BrdU-substituted (TB) chromatids appeared somewhat more severely collapsed than the bifilarly substituted (BB) chromatids. Subsequent Giemsa staining, however, brought about pronounced piling up of the Giemsa dye on the TB-chromatids but not on the BB-ones, causing highly distinct differential Giemsa staining as well as a marked differentiation in surface topography between the sister chromatids. Removal of the Giemsa dye from the differentially Giemsa stained chromosomes resulted in a disappearance of such a pronounced topographic differentiation.     

Purification and subunit structure of RNA polymerase II from the pea.

DNA-dependent RNA polymerase II (EC 2.7.7.6) from pea seedlings (Pisum sativum var. Alaska) has been purified to homogeneity, as judged by native polyacrylamide electrophoresis. The procedure includes polyethyleneimine precipitation and elution, ammonium sulfate precipitation, DEAE-Sephadex chromatography, phosphocellulose chromatography, and heparin-Sepharose chromatography. The enzyme purified almost to homogeneity has a specific activity of 200 nmol/mg per 15 min at 30 degrees C with denatured calf thymus DNA as template. The enzyme activity is 50% inhibited in the presence of 0.05 migrograms/ml of alpha-amanitin. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicates that pea RNA polymerase II is composed of eight subunits with molecular weights and molar ratios (in parentheses) of 170 000 (0.9), 140 000 (1.0), 43 000 (1.5), 26 000 (2.0), 22 500 (1.2), 21 500 (0.6), 18 500 (1.6) and 17 500 (2.3). The structure is closely similar to that of cauliflower RNA polymerase II.     

Inhibitory effect of amines on polar filament extrusion byPlistophora anguillarum spores

In in vitro tests, amines were screened for the inhibition of polar filament extrusion by spores ofPlistophora anguillarum, a microsporidian parasite of the eel. Primary amines having C₈ ⁻ C₁₈ alkyl chains were effective, irrespective of the anions bound. Secondary amines having a branched C₈ chain and tertiary amines having C₁₄−C₁₈ chains were also effective. Asymmetry in side chains seemed to be required for inhibitory action. Quaternary ammonium salts having C₁₂−C₁₆ alkyl chains and some germicides or disinfectants such as cetyl pyridinium chloride and benzethonium chloride were also effective. Diamines and amides were ineffective regardless of the length of their alkyl chins. In in vivo tests, eel larvae-fed for 4 days with a commercial feed supplemented with 5×10⁸ cells of spores and 4g of laurylamine aspartate/100 g feed, and thereafter with the usual commercial feed for 26 days—were not infected.     

A new assay system of phospholipid exchange activities using concanavalin a in the separation of donor and acceptor liposomes

A new assay system of phospholipid exchange activities is described. The exchange activities were quantitated by measuring the stimulation of phospholipid transfer between two separate populations of liposomes, which contained, as the major constituents, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, and cholesterol in molar ratios of 6: 2: 1: 1: 5. One population of the liposomes was made reactive to concanavalin A by the incorporation of 1.8 mol% $\text{α-}\text{d}\text{-mannosyl}\text{-(1 → 3)-α-}\text{d}\text{- mannosyl}\text{-sn-}\text{1,2-diglyceride}$ from Micrococcus lysodeikticus. The concanavalin A-reactive liposomes, a phospholipid donor, were doubly labelled with [6-³H]galactosylglucosyl ceramide and that class of ³²P-labelled phospholipids whose exchange was being measured. The ³H-labelled glycolipid served as a non-exchangeable reference marker. The other population of the liposomes, a phospholipid acceptor, was concanavalin A nonreactive. These two populations of liposomes were incubated with the cytosol protein of rat liver in a total volume of 0.2 ml.After the incubation, two different procedures were used to separate the two liposomal populations. In one procedure concanavalin A was added to agglutinate the reactive liposomes; the flocculated lectin-liposome complex was separated from the non-reactive liposomes by brief centrifugation. In the other procedure the reactive liposomes were trapped by binding to concanavalin A covalently coupled to Sepharose 2B; the complex was separated from the nonreactive liposomes by filtration through a filter paper under suction. In both assay procedures the amount of phospholipid transferred from the donor to the acceptor liposomes was calculated from the decrease of ³²P/³H ratio of the concanavalin A-reactive liposomes during the incubation. By the assay system it is possible to determine phosphatidylcholine and phosphatidylinositol exchange activities in 100 μg of rat liver cytosol protein.