Urea-induced transformation of native estrogen receptor and evidence for separate DNA-and ATP-binding sites

We have investigated the involvement of hydrophobic receptor domains during transformation of the native estrogen receptor to a form(s) with high affinity for immobilized DNA and ATP. In the presence of 6 M urea the intact estrogen-receptor complex was completely (greater than 90%, n = 12) transformed into a DNA-binding configuration but only partially (35-45%, n = 8) transformed into an ATP-binding state. Similar experiments performed with unliganded receptor preparations further distinguished the receptor's DNA and ATP binding properties. While the urea-induced increase in receptor affinity for DNA-agarose was estrogen-dependent, the urea-induced increase in affinity for ATP-agarose was steroid-independent. This is the first direct evidence that hydrophobic receptor domains may be involved in the steroid-dependent exposure of the DNA binding site. This event is partially reversible and suggests that electrostatic interactions alone may not be sufficient to accurately describe receptor recognition of specific DNA acceptor sites.     

T and B cells induce macrophages which suppress proliferation but not lymphokine secretion

In vitro culture of mouse spleen cells for 2 days or more leads to the production of adherent, phagocytic, Thy-1-, Ia+, Lyt-2- cells ("suppressor macrophages") which strongly inhibit the proliferative response of T and B lymphocytes to a variety of stimuli: mitogens, specific antigens, and antigen-nonspecific growth factors. Suppressive activity fails to develop, however, in cultured spleen cells from which nonadherent cells have been removed before the initial 48-hr incubation, and only partial suppression is obtained from cell suspensions from which T cells have been depleted before culture. We find that the requirement for nonadherent cells can be replaced by graded doses of lymphocytes. Lyt-2- and Lyt-2+ T cells are about equally potent in inducing suppressive activity in nonadherent cells. Surprisingly, B cells (containing fewer than 0.1% contaminating T cells) are also able to induce suppression in this system. The suppression induced includes both indomethacin-sensitive and indomethacin-resistant components. Interestingly, not all stages of mitogen-induced T-cell activation are blocked by these adherent cells: proliferation is inhibited, but production of interleukin 2 (IL-2) and interleukin 3 (IL-3) is unaffected.     

Effect of physico-chemical factors on anion-sensitive ATPase activity

Effects of temperature, pH and anions on the ATPase activity of submitochondrial particles of rat liver, rat heart, mouse liver, of red blood cell membranes, and of soluble enzyme of rat liver, mouse liver mitochondria were studied. The temperature relationships of membrane-bound and soluble ATPases have the breaks at 18-21 degrees C and 30-32 degrees C. These breaks were not shifted by sulfite, thiocyanate, methanol, glycerol and GTP. The pH changes from 6.0 to 8.5 produced no effect on the temperature relationships of ATPase activities but, strongly influenced the rate of ATPase reaction. The conformity between the obtained data and earlier proposed mechanism of anion control over anion-sensitive ATPase activity was discussed.     

A modified method of UDS detection in vitro suitable for screening the DNA-damaging effects of chemicals

The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test.     

The influence of ovarian hormones on the rat oviductal and uterine concentration of noradrenaline and 5-hydroxytryptamine

This paper describes the effects of estradiol and progesterone on the concenirations of noradrenaline and 5-hydroxytryptamine in the Wistar rat oviduct and uterus. The levels of noradrenaline and 5-hydroxytryptamine are higher in the oviduct than in the uterus whereas p-tyrosine and tryptophan are similar in both tissues. Estradiol treatment reduced the oviductal concentration of noradrenaline but not 5-hydroxytryptamine in oviduct, while the concentrations of both noradrenaline and 5-hydroxytryptamine were reduced in uterine horn. The levels of noradrenaline in the oviduct and uterus in rats in estrus were lower than those of diestrous rats. Bilateral ovariectomy produced an increase in uterine noradrenaline and 5-hydroxytryptamine levels. These changes were reversed in the presence of ovarian hormones as indicated by experiments where unilateral ovariectomy was performed. Reserpine administration reduced noradrenaline concentration in both the oviduct and the uterus but did not change oviductal or uterine 5-hydroxytryptamine.These results indicate the existence of noradrenaline within postganglionic sympathetic nerve terminals and suggest that estrogens increase the utilization and the synthesis of noradrenaline in both the oviducts and the uterine horns. With respect to 5-hydroxytryptamine the data support the concept that it is mainly associated with mast cells.