Proceedings of the National Academy of Sciences of the United States of America
-
Proc. Natl. Acad. Sci. U.S.A. · Oct 1981
5'-O-Monophosphoryladenylyl(2' goes to 5')adenylyl(2' goes to 5')adenosine is an antagonist of the action of 5'-O-triphosphoryladenylyl-(2' goes to 5')adenylyl(2' goes to 5')adenosine and double-stranded RNA.
5'-O-Monophosphoryladenylyl(2' goes to 5')adenylyl-(2' goes to 5')adenosine [(2' goes to 5')(pA)3] antagonizes the protein synthesis inhibitory effects of 5'-O-triphosphoryladenylyl-(2' goes to 5')adenylyl(2' goes to 5')adenosine by preventing activation of the (2' goes to 5')oligo(a)-activated ribonuclease which degrades mRNA. The oligoribonucleotide (2' goes to 5')(pA)3 also antagonizes the translational inhibitory capacity of poly(I).poly(C) in extracts of interferon-treated L cells, suggesting that (2' goes to 5')oligo(A) is the primary mediator of the protein synthesis inhibitory effects of poly(I).poly(C) in this cell-free system.
-
Proc. Natl. Acad. Sci. U.S.A. · Nov 1979
Induction of calcium flux across the rat mast cell membrane by bridging IgE receptors.
Rabbit antibody against IgE receptors or its F(ab')2 fragments induced an increase of 45Ca uptake into normal mast cells, and this process was accompanied by histamine release. Evidence was obtained that a substantial portion of 45Ca uptake was due to movement of calcium across the cell membrane. ⋯ However, bridging of receptor-bound Fab' fragments by antirabbit IgG or bridging of receptor-bound IgE by anti-IgE induced an increase in 45Ca uptake. The results collectively indicate that crosslinking IgE receptors increases the membrane permeability of the mast cells toward calcium.
-
Proc. Natl. Acad. Sci. U.S.A. · Nov 1979
Crossreactive mixed lymphocyte reaction determinants recognized by cloned alloreactive T cells.
We have isolated clones of alloreactive T cells by soft agar cloning of primed responder cells contained in serially restimulated, mixed lymphocyte cultures. These clones recognize unique mixed lymphocyte reaction (MLR) stimulating determinants present on (C57B/6 X A/J)F1 (B6A) spleen cells. ⋯ Using such clones of alloreactive T cells, we have identified and are attempting to define crossreactive MLR stimulating determinants exhibited by a panel of stimulator cells. Recognition by certain clones of a shared MLR determinant(s) on B6A and DBA/2 and of the lack of this determinant(s) on B6 stimulator cells questions current concepts concerning the nature of MLR stimulating determinants and T cell recognition of alloantigens.
-
Proc. Natl. Acad. Sci. U.S.A. · Apr 1978
Opposing effects of estradiol and progesterone on oxytocin receptors in rabbit uterus.
Estradiol-17beta administration to young (10- to 12-week-old) rabbits to produce the "estrogen-dominated" uterus increased the uterine contractile response to both oxytocin and methacholine in vitro. In "progesterone-dominated" uteri, obtained from rabbits that received progesterone for 4 days after estrogen pretreatment, the contractile response to oxytocin in vitro was selectively abolished; the response to methacholine was unaffected. Parallel changes were observed in the concentration (but not affinity) of specific sites in uterine microsomal membranes that bind [(3)H]oxytocin with selectivity features expected for oxytocin receptors. ⋯ These results suggest that the regulatory effects of estrogens and progesterone upon the rabbit uterine contractile response to oxytocin are achieved, at least in part, by the opposing actions of these steroids in regulating the number of oxytocin receptors in smooth muscle cells. Estradiol increased the concentration of uterine oxytocin receptors; the maintenance of high receptor levels appears to depend upon the continuous de novo synthesis of oxytocin receptors. In contrast, progesterone, like actinomycin D, appears to act at the nuclear locus to repress synthesis of oxytocin receptors.
-
Proc. Natl. Acad. Sci. U.S.A. · Feb 1978
Incomplete dosage compensation in an evolving Drosophila sex chromosome.
Cellular autoradiography was used to measure relative rates of chromosomal RNA synthesis and to examine the regulatory phenomenon of X-linked dosage compensation in Drosophila miranda, a species containing two distinct, nonhomologous X chromosomes (X1 and X2). The X1 chromosome was found to be dosage-compensated, since the rate of RNA synthesis along the single X1 chromosome in males equaled that of both X1 chromosomes in females. ⋯ Our data are consistent with the idea that the evolution of X2 dosage compensation has paralleled the differentiation of the X2 sex chromosome. In addition, gene rearrangement seems to have accompanied the acquisition of a dosage-compensory mechanism in the X2.