Live-cell three-dimensional single-molecule tracking reveals modulation of enhancer dynamics by NuRD

To understand how the nucleosome remodeling and deacetylase (NuRD) complex regulates enhancers and enhancer-promoter interactions, we have developed an approach to segment and extract key biophysical parameters from live-cell three-dimensional single-molecule trajectories. Unexpectedly, this has revealed that NuRD binds to chromatin for minutes, decompacts chromatin structure and increases enhancer dynamics. We also uncovered a rare fast-diffusing state of enhancers and found that NuRD restricts the time spent in this state. Hi-C and Cut&Run experiments revealed that NuRD modulates enhancer-promoter interactions in active chromatin, allowing them to contact each other over longer distances. Furthermore, NuRD leads to a marked redistribution of CTCF and, in particular, cohesin. We propose that NuRD promotes a decondensed chromatin environment, where enhancers and promoters can contact each other over longer distances, and where the resetting of enhancer-promoter interactions brought about by the fast decondensed chromatin motions is reduced, leading to more stable, long-lived enhancer-promoter relationships.

The Nucleosome Remodeling and Deacetylase Complex NuRD Is Built from Preformed Catalytically Active Sub-modules

The nucleosome remodeling deacetylase (NuRD) complex is a highly conserved regulator of chromatin structure and transcription. Structural studies have shed light on this and other chromatin modifying machines, but much less is known about how they assemble and whether stable and functional sub-modules exist that retain enzymatic activity. Purification of the endogenous Drosophila NuRD complex shows that it consists of a stable core of subunits, while others, in particular the chromatin remodeler CHD4, associate transiently. To dissect the assembly and activity of NuRD, we systematically produced all possible combinations of different components using the MultiBac system, and determined their activity and biophysical properties. We carried out single-molecule imaging of CHD4 in live mouse embryonic stem cells, in the presence and absence of one of core components (MBD3), to show how the core deacetylase and chromatin-remodeling sub-modules associate in vivo. Our experiments suggest a pathway for the assembly of NuRD via preformed and active sub-modules. These retain enzymatic activity and are present in both the nucleus and the cytosol, an outcome with important implications for understanding NuRD function.

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We have studied Drosophila nucleosome remodeling deacetylase (NuRD) assembly.

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NuRD consists of a core deacetylase complex, where MTA-like acts as the scaffold.

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This transiently associates with a chromatin remodeling sub-module including CHD4.

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Single-molecule imaging shows that the two sub-modules associate through MBD-like.

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NuRD comprises catalytically active sub-modules in both the cytosol and the nucleus.

Transition between isozymic forms of enolase during in vitro differentiation of neuroblastoma cells-II

An analysis of enolase expression during differentiation of neuroblastoma clones in homogeneous culture is presented. The enolases expressed in these neuroblast-like cells are identical to those of mouse brain with respect to the examined properties. Our biochemical investigation has premitted us to demonstrate formally that neuroblastoma cells undergo a transition from the embryonic ?? form to the neuronal ?? form and contain both enolases as well as the ?? hybrid form during maturation. These results suggest that the same phenomenon must exist in vivo for neuroblasts. In neuroblastoma cells, an increase in both ?? and ?? neuron specific enolases is related to cell maturation and expression of the ?? form precedes that of the ?? form during differentiation. Modulation of neuronal enolase activities is similar in the various conditions of differentiation studied and appears not to be necessarily related with morphological differentiation, although concomitant with an arrest of cell division. The evolution of specific neuronal enolases in neuroblastoma cells parallels that observed in vivo, in brain from embryonic day 15 to post-natal day 7. Moreover, at least one treatment (dimethylsulfoxide) causes an important decrease in the high specific ?? activity of these cells as occurs in vivo. This enolase can therefore also be considered as a biochemical marker for neuroblastoma maturation. As observed with other markers and other cell types, neuroblastoma cells in culture express an immature biochemical differentiation of the enolase isozymes.

A redox mechanism controls differential DNA binding activities of hypoxia-inducible factor (HIF) 1alpha and the HIF-like factor

Hypoxia-inducible factor 1alpha (HIF-1alpha) and the HIF-like factor (HLF) are two highly related basic Helix-Loop-Helix/Per-Arnt-Sim (bHLH/PAS) homology transcription factors that undergo dramatically increased function at low oxygen levels. Despite strong similarities in their activation mechanisms (e.g. they both undergo rapid hypoxia-induced protein stabilization, bind identical target DNA sequences, and induce synthetic reporter genes to similar degrees), they are both essential for embryo survival via distinct functions during vascularization (HIF-1alpha) or catecholamine production (HLF). It is currently unknown how such specificity of action is achieved. We report here that DNA binding by HLF, but not by HIF-1alpha, is dependent upon reducing redox conditions. In vitro DNA binding and mammalian two-hybrid assays showed that a unique cysteine in the DNA-binding basic region of HLF is a target for the reducing activity of redox factor Ref-1. Although the N-terminal DNA-binding domain of HIF-1alpha can function in the absence of Ref-1, we found that the C-terminal region containing the transactivation domain requires Ref-1 for full activity. Our data reveal that the hypoxia-inducible factors are subject to complex redox control mechanisms that can target discrete regions of the proteins and are the first to establish a discriminating control mechanism for differential regulation of HIF-1alpha and HLF activity.

IFN-gamma treatment of rodents infected with erythrocytic stages of Plasmodium chabaudi: differential effects according to the immunological status

Recombinant rat interferon-gamma (rrIFN-gamma) was tested for its antimalarial activity in three different models of Plasmodium chabaudi-blood stage malaria. Doses ranging from 1 x 10(4) to 1 x 10(5) U of rrIFN-gamma were used in each model. In BALB/c mice (lethal infection), prophylactic treatment with daily intraperitoneal (i.p.) injections reduced parasitemia and delayed mortality. In contrast, subcutaneous administration of rrIFN-gamma was inefficient, as was curative schedule of i.p. administration. Euthymic Fischer rats, which develop an acute and resolutive infection, were partly protected by i.p. prophylactic administration of rrIFN-gamma. Parasitemia was reduced without being lengthened, resulting in a marked decrease in parasite burden. Subcutaneous administration was less efficient whereas curative schedule was not. Athymic (nude) Fischer rats which present a longlasting and stable infection were treated with prophylactic and curative schedules of i.p. administration of rrIFN-gamma. In each case, rrIFN-gamma-treated nude rats, as control nude rats, were unable to resolve their chronic infection. The conditions required to obtain a beneficial effect are thus restrictive for a therapeutic use in humans. Moreover, these results show that, despite the fact that IFN-gamma is considered as a major component of the immune response, this cytokine alone is not sufficient to induce the totality of the effector mechanisms necessary to cure malarial infections.

Effects of low dose total body irradiation (LDTBI) and recombinant human interleukin-2 in mice

10-16-Week-old female BALB/c mice received low dose total body irradiation (LDTBI) in one fraction immediately before the beginning of treatment with recombinant human interleukin-2 (rIL-2). LDTBI prevented in a dose-dependent manner the weight increase of the spleen, liver and lungs induced by fluid extravasation provoked by rIL-2 injections. It also limited the increase of the number of mononuclear cells in the spleen induced after in vivo treatment with rIL-2. Immunofluorescence analysis of spleen cells revealed that LDTBI decreased the relative sIgM+ cell number in spleen, while the relative numbers of Lyt-1+, Thy-1+ and L3T4+ cells were increased, indicating that a T and/or NK population, radioresistant to LDTBI, could still proliferate under rIL-2 stimulation in vivo. Such lymphocytes were capable of in vitro lysis of YAC cells in a 4-hour 51Cr release assay, as well as lymphokine-activated killer (LAK) cells obtained in mice treated with rIL-2 alone. Thus, LDTBI given prior to rIL-2, yet preserving the cytotoxic capacity of the LAK cells activated by rIL-2, could prevent the vascular leak syndrome toxicity induced by rIL-2 injection.

Use of monoclonal antibodies for discrimination between natural and recombinant human interferon-tau

Different monoclonal antibodies (MAbs) were raised against denaturated and native recombinant human Interferon-tau (IFN-tau). This approach gave us MAbs which recognized either N-term (prepared with SDS-denaturated IFN-tau) or C-terminal part of the antigen as well as MAbs which linked to non linear epitopes (obtained with native form of IFN-tau). Some of them inhibited or enhanced their respective binding to IFN-tau. After characterization, these antibodies were used as probes and some were selected to prepare two quantitative sensitive sandwich IRMAs able to discriminate between recombinant and natural IFN-tau.

Antitumor activity of gamma-interferon in ascitic and solid tumor models of human ovarian cancer

We have investigated the action of recombinant human gamma-interferon (rHuIFN-gamma) against human ovarian cancer xenografts growing as ascites or as bulky solid i.p. tumors in nude mice. Both forms of the disease responded to i.p. rHuIFN-gamma with significant increases in mouse survival time, and in 2 of 3 ascitic models the mice were cured of peritoneal disease. The activity of rHuIFN-gamma was dose and schedule dependent, and xenografts derived from 3 different patients showed a heterogeneity of response. Peak i.p. levels of rHuIFN-gamma in nude mice bearing multiple i.p. solid tumors were similar to those found in ovarian cancer patients receiving i.p. rHuIFN-gamma, but clearance was more rapid in the mice. Rat gamma-interferon had no antitumor activity at the same doses and schedules although it had some biological activity in the nude mice. Histological examination of treated tumors revealed increased necrosis and loss of cellular organization with large areas of hypocellular epithelial mucin. These changes were preceded by a fall in tumor tryptophan and a rise in tumor kynurenine. We conclude that rHuIFN-gamma has a direct dose related antitumor effect on ovarian cancer xenografts that is preceded by increased metabolism of tryptophan.

Autocrine stimulation of interleukin 1 in human adherent synovial lining cells: down regulation by interferon gamma

Interleukin 1 (IL-1) exerts biological properties on various immune and nonimmune cell types and tissues and thus may play an important role during chronic inflammatory processes. Here we have examined the IL-1 biosynthesis in adherent synovial lining cell (ASLC) cultures obtained from patients with rheumatoid arthritis (RA). We report that ASLCs in culture showed heterogeneous endogenous levels of IL-1 alpha and beta expression. Recombinant interleukin 1 (rIL-1) alpha or beta induced increases of IL-1 alpha and beta mRNA and proteins levels in ASLCs. Although IL-1 synthesis is enhanced by rIL-1 treatment, no soluble IL-1 alpha or beta could be detected by specific enzyme-linked immunosorbent assays. A pretreatment with recombinant IFN gamma (rIFN gamma) down-regulated the effect of rIL-1 on IL-1 synthesis in ASLCs. Actinomycin D suppressed the endogeneous and rIL-1-induced IL-1 mRNA expression Indomethacin, in the presence of rIL-1 alpha or beta, up-regulates the level of expression of IL-1 beta in ASLCs pretreated with rIFN gamma, but has the opposite effect in non-pretreated cells. The increase of IL-1 gene expression by rIL-1 in human ASLCs from RA patients may contribute as an amplification of the disease progress. These studies may also explain the beneficial effects of IFN gamma in experimental models of IL-1-induced bone and cartilage degradation and in patients with diseases involving IL-1.

Sucrose phosphate synthase, a key enzyme for sucrose biosynthesis in plants: protein purification from corn leaves and immunological detection

We have purified the protein for the enzyme sucrose phosphate synthase (SPS) from corn (Zea mays) leaves. Partially purified SPS protein was used to generate specific monoclonal antibodies. The following immunoaffinity chromatography allowed the isolation of pure SPS protein. The apparent molecular mass of the SPS polypeptide is 138 kilodaltons. By immunoblot, an SPS antigen was found to accumulate in mature leaves. SPS protein levels remain constant during the day/night cycle. The observed diurnal fluctuation of extractable enzyme activity, therefore, must be caused by modification of the specific activity of SPS in vivo.

Role of interferon-gamma on the in vivo expression of functional interleukin-2 receptors by murine macrophages

Interferon-gamma activates both in vitro and in vivo macrophage functions. Injection of rat recombinant interferon-gamma (rR-IFN-gamma) induced the expression of interleukin-2 receptors (IL-2R) by peritoneal macrophages from normal BALB/c and MRL-+/+ mice. Moreover, rR-IFN-gamma stimulated in a dose-dependent manner the oxidative burst of cells as revealed by luminol-dependent chemiluminescene (LDCL). Resident peritoneal macrophages from MRL-lpr/lpr (mice that develop a systemic lupus-like syndrome) showed a higher PMA-triggered LDCL response. This enhanced activity was accompanied by an increase in IL-2R expression (30% vs. less than 1%). The "activated" macrophages from rR-IFN-gamma-treated normal mice as well as MRL-lpr/lpr mice did not respond to the addition of recombinant interleukin-2 (rHu-IL-2) by an increase in LDCL. However, rHu-IL-2 triggering became efficient when cells enriched in IL-2R-bearing macrophages were preincubated overnight with rHu-IL-2R. This response may point out a functional role for IL-2R and provide a role for IL-2 in certain macrophage functions.

21.1.1, a novel activation marker of T and B cells

A new rat mAb designated mAb 21.1.1 was raised against a T cell hybridoma of mouse origin, T2D4. This antibody, an IgG2b, immunoprecipitates from the membrane extracts of iodinated T2D4 cells a 56-kDa glycoprotein of apparent pI 4.6 which gives a 34-kDa polypeptide after treatment with endoglycosidase F. MAb 21.1.1 reacts with an antigen expressed on murine mitogen-activated thymocytes and T cells, and on B cells stimulated by anti-IgM antibodies. Cells isolated from the spleen, lymph nodes and bone marrow are negative, as are purified resting B cells or T cells. This antigen is strongly expressed on most day-16 fetal thymocytes whereas adult thymocytes are almost negative. mAb 21.1.1 may be useful for the study of activation and differentiation of T and B cells.

Effect of rIFN-gamma and IL-2 treatments in mouse and nude rat infections with Toxoplasma gondii

Mice and nude rats lethally infected with T. gondii and treated with recombinant rat interferon-gamma (rIFN-gamma) or recombinant human interleukin-2 (rIL-2) were protected against death, when compared with untreated infected controls. In mice rIFN-gamma and rIL-2 played an important role in "prophylactic treatment", but not in "curative therapy". The survival rate was 42% in mice treated with 3 doses of 20,000 U of rIFN-gamma at days -2, -1, 0 before challenge and up to 66% in mice treated with 3 doses of 10,000 U of rIFN-gamma at days -2, 0, +2 before and after infection. Whereas the survival rate was 33% in mice that received 3 doses of 500 U rIL-2 at days -2, -1, 0 before infection, or -2, 0, +2 before and after infection respectively, up to 50% of the mice treated with 3 doses of 1,000 U rIL-2 at days -2, -1, 0 survived. In nude rats rIFN-gamma had a slight effect in "prophylactic treatment", whereas rIL-2 was active only in "curative treatment". The survival rate was 25% both in nude rats treated with doses of 400,000 U of rIFN-gamma at days -3, 0 before challenge, or with doses of 5,000 U of rIL-2 at days +2, +6, +9 after infection. These results lead us to hypothesise that the mechanism by which the lymphokine treatment exerts a protective effect on Toxoplasma infected mice is different from that on nu/nu rats. We conclude that these cytokines may play a notable role in modulating the host's immune defence against T. gondii infection.

Recombinant human interleukin-1 beta primes human polymorphonuclear leukocytes for stimulus-induced myeloperoxidase release

Recombinant human Interleukin-1 (rhIL-1) beta was found to enhance stimulus-induced granule exocytosis from human polymorphonuclear leukocytes (PMNs). PMNs were incubated with rhIL-1 beta and then stimulated with either heat-aggregated IgG (Hagg) or N-formyl-methionyl leucylphenylalanine (FMLP). The release of the azurophil enzyme myeloperoxidase (MPO) was measured. Low concentrations of stimuli (10 micrograms/ml Hagg, 2.5 X 10(-9) M FMLP) did not stimulate degranulation in the absence of rhIL-1 beta. However, such concentrations elicited marked degranulation from PMNs preincubated with rhIL-1 beta (0.2-100 ng/ml). The enhancement of degranulation was dependent on the concentration of rhIL-1 beta employed and on the period of incubation. In other experiments, the effect of rhIL-1 beta on the PMN oxidative response was determined. rhIL-1 beta did not directly stimulate the production of superoxide anions or enhance the oxidative response to Hagg or FMLP. It is suggested that in rheumatoid joints, IL-1 beta may potentiate PMN degranulation, but not their oxidative response.

Interferon-gamma (IFN-gamma) and interleukin-2 in the generation of lymphokine-activated killer cell cytotoxicity--IFN-gamma-induced suppressive activity

Incubation of human lymphocytes with recombinant interleukin-2 (rIL-2) results in the generation of lymphokine-activated killer (LAK) cells capable of lysing a wide variety of tumor cells. The present study was undertaken to examine the effect of recombinant gamma interferon (rIFN-gamma) on LAK cell cytotoxicity generated from different peripheral blood mononuclear cell (PBMC) subpopulations. When unseparated PBMC were stimulated by rIL-2 and rIFN-gamma, the latter induced a transient enhancement after 2 days followed by a suppression of LAK cell cytotoxicity at day 6. Enhancement of LAK cell cytotoxicity was moderate and inconstant, whereas the inhibition was strong and observed with all the donors tested. This suppression was not associated with a decrease in the [3H]thymidine uptake. PBMC depleted of adherent cells were more sensitive to the stimulation by rIL-2 and the induced cytotoxicity was not modified by rIFN-gamma. Monocyte-enriched plastic-adherent cells, when incubated with rIL-2 and rIFN-gamma, became cytotoxic after 2-3 days of culture and inhibited LAK cell activity after 5-6 days. Collectively, our results suggest that rIFN-gamma affects LAK cell cytotoxicity through the activation of plastic-adherent, monocyte-rich, cells which modulate natural killer cells, first in a positive, then in a negative way.

Opposite effect of Interferon-gamma on PGE2 release from Interleukin-1-stimulated human monocytes or fibroblasts

Stimulated monocytes produce prostaglandins (PGE2) in response to lipopolysaccharide (LPS), Muramyl dipeptide (MDP) or Interleukin-1 (IL-1). This response could be modulated in different ways by Interferon-gamma (IFN-gamma). This lymphokine, known to potentiate IL-1 production by LPS- or MDP-stimulated monocytes, suppressed different Il-1 activities such as PGE2 release by the same cells. By contrast, an impairement of suppression by IFN-gamma was evidenced in rIL-1 beta-induced PGE2 release from human dermal fibroblasts. Salmon calcitonin (sCT), another inhibitor of IL-1-induced bone resorption, was able to prime monocytes to potentiate PGE2 elaboration by LPS, but failed to modulate PGE2 liberation from either rIL-1 beta-stimulated monocytes or fibroblasts.

Interferon gamma is active on human lymphoblastoid Namalva cells without inducing an antiviral state

We demonstrate the presence of high affinity receptors specific for interferon-gamma (IFN-gamma) in human lymphoblastoid Namalva cells. The presence of these receptors, whose binding affinity and cross-linking characteristics were not distinguishable from those of the corresponding receptors in sensitive cells, was not consistent with the lack of responsiveness of Namalva cells to IFN-gamma as regards growth inhibition, induction of 2'-5' oligoadenylate synthetase activity and inhibition of virus multiplication. Nevertheless, IFN-gamma enhanced the expression of two genes, HLA class II and c-myc. Although the mechanism of these IFN-gamma-mediated modifications is not understood, these results provide evidence that the IFN-gamma receptors present in Namalva cells are functional.

Effect of in vivo injection of recombinant human interleukin-2 on peritoneal macrophages from MRL-lpr/lpr mice

Different characteristics of peritoneal macrophages have been studied, to assess the role of macrophages in the pathogenesis of MRL-lpr/lpr mice which develop a lupus-like syndrome. Resident peritoneal macrophages from MRL-lpr/lpr mice (greater than 10 weeks old) displayed characteristics of activation, while thioglycollate-elicited or resident macrophages from normal mice (Balb/c or MRL-+/+) did not. In addition to Ia antigens, macrophages spontaneously expressed Interleukin-2 receptors (IL2-R) whereas resident macrophages from normal mice did not. Injection of recombinant human Interleukin-2 (rHu-IL2) by the i.p. route to normal mice did not modify the cellular composition of the resident peritoneal population. On the contrary, rHu-IL2 treatment of MRL-lpr/lpr mice induced an enhancement in cell number in the peritoneal cavity. At the same time, macrophages harvested from treated MRL-lpr/lpr mice showed enhanced chemiluminescence triggered by phorbol-12-myristate-13-acetate (PMA) whereas peritoneal macrophages from treated normal mice did not. These results indicate that MRL-lpr/lpr peritoneal macrophages display features of selective 'activation' and suggest that the expression of IL2-R could be involved in the pathogenesis of inflammatory disorders seen in MRL-lpr/lpr autoimmunity.

Further evidence for the presence of specific binding sites for prolactin in the rabbit brain. Preferential distribution in the hypothalamus and substantia nigra

In the present research we have extended our work on the presence of binding sites for prolactin in the rabbit brain focusing our attention on the brain areas with high dopamine cell bodies density. Among these areas the hypothalamus showed the highest specific binding of labeled ovine prolactin (oPRL). Clearly detectible specific binding was observed also in substantia nigra, whereas in other brain regions the specific binding was very small, except for the striatum where a low but not negligible binding was found in female rabbits. The binding of 125I-oPRL showed a hormonal specificity and Scatchard analysis of the binding showed no clear difference in dissociation constant (Kd) between hypothalamus, nigra and striatum.

Presence and characterization of prolactin receptors in human benign breast tumours

Prolactin receptors have been determined in 64 benign breast tumours. A specific binding of 0.5% or more (with a range of 0.5-3.3%) was found in 34.4% of the cases and was considered prolactin-receptor-positive. The binding was found to be specific only for lactogenic hormones. By Scatchard analysis the dissociation constant was 2.55 X 10(-10) mol/l and the binding capacity was 4.6 fmol/mg protein.

Modifications in prolactin binding capacity in the rat liver induced by non-steroidal anti-inflammatory drugs

Modifications in prolactin specific binding in the rat liver induced by different non-steroidal anti-inflammatory drugs (indomethacin, piroxicam, ketoprofen, phenylbutazone, mefenamic acid and acetylsalicylic acid) have been studied. All caused a dose-dependent inhibition of prolactin binding capacity whereas no change was found in dissociation constant values. The inhibitory effect is reversible and highly specific, since insulin binding to the same membrane preparation is not affected. The degree of inhibitory activity on prolactin binding is related to the anti-inflammatory activity of each drug, which supports the hypothesis of an involvement of prostaglandin synthesis.

Glucocorticoids modulate the response of ornithine decarboxylase to unilateral removal of the dorsal hippocampus

The effect of unilateral removal of the dorsal hippocampus and of glucocorticoid administration was measured on the activity of ornithine decarboxylase (ODC) in the remaining contralateral hippocampus lobe. Unilateral hippocampectomy (Hx) resulted in a rapid rise of ODC activity in the contralateral lobe. The effect on ODC was maximal at 6 h after surgery and lasted two days. In the absence of the adrenals the effect of Hx on the enzyme was more potent and more prolonged. Elevated ODC activity was still detectable at 5 days after surgery, but not at 10 days. Chronic replacement with dexamethasone (DEX) offered in drinking water decreased the Hx-induced ODC response of ADX rats at 3 days after surgery to the level of enzyme activity observed in the S-ADX Hx subject. The effect of the steroid seemed related to the extent of occupation of the pool of glucocorticoid receptor sites in cytosol of rat hippocampus. In contrast, a single injection of a high dose of DEX to Hx-ADX animals at 3 days after surgery increased ODC activity in addition to the lesion-induced ODC in the contralateral lobe. It is concluded that after unilateral removal of the dorsal hippocampus ODC is a biochemical marker for cellular responses taking place in the contralateral lobe. Glucocorticoids modulate the lesion-induced ODC response.

Physiological and pharmacological variations in rabbit prolactin plasma levels

By using a specific homologous double-antibody RIA, physiological and pharmacological variation in prolactin plasma levels were studied in the rabbit. The study of plasma levels during 24 h period demonstrated the presence of a rhythmic secretion of prolactin with higher values between 15.00 and 19.00 h. Prolactin plasma levels were low in neonatal rabbits and increased gradually with the age of the animals. In adult rabbits a significant higher prolactin plasma concentration was found in female animals. Blood levels fluctuate during the first half of pregnancy but the mean levels were higher than those found during the second half of gestation. A remarkable increase of plasma levels was observed 24 h before parturition and during lactation. Plasma prolactin concentrations increased after injection of both chlorpromazine and sulpiride. The hyperprolactinaemic effect of sulpiride was abolished by bromocriptine.

Ornithine decarboxylase induction by glucocorticoids in brain and liver of adrenalectomized rats

Ornithine decarboxylase (ODC), the rate-limiting enzyme in the biosynthesis of polyamines, was measured in the brain and the liver of adrenalectomized rats after an acute s.c. treatment with glucocorticoids. The effects of corticosterone and dexamethasone were compared in three brain areas, the cerebral cortex, hippocampus, and cerebellum. These structures have similar concentrations of cytosolic glucocorticoid receptor, as measured by an in vitro exchange assay using a specific glucocorticoid ligand, [3H]RU 26988, but contain different amounts of mineralocorticoid receptor. Corticosterone and dexamethasone increased ODC activity in the liver and brain areas in a dose-dependent manner, dexamethasone being more active than corticosterone in all tissues. Moreover, estradiol, progesterone, and testosterone were inactive. Aldosterone, at high doses, increased brain ODC activity. Glucocorticoids, selected for their weak binding, or lack of binding to the mineralocorticoid receptor, were tested and found to be highly active in inducing brain and liver ODC, thus showing that ODC induction by steroids is specific for glucocorticoids. These results are among the first to suggest biochemically a central action of glucocorticoids following an acute treatment and confirm that the brain is a glucocorticoid target organ.

Adrenocorticotropin analogs and glucocorticoids in the hypophysectomized rat. II. Effects on cerebral cortex polyribosomes

The capacity of free polyribosomes from rat cerebral cortex to incorporate labeled amino acids into protein (polyribosome activity) was compared in normal, hypophysectomized, and treated hypophysectomized rats. Polyribosome activity was measured in a cell-free system using a pH 5 supernatant from sham-operated rats. The polyribosome activity of hypophysectomized rats was 10-20% less than that of sham-operated rats. Subcutaneous treatment of hypophysectomized rats daily for 10 days with ACTH, corticotropic ACTH fragments [10-2- microgram of ACTH-(1-24), ACTH-(1-23), or Hoe 433 (ACTH-(1-17))], or glucocorticoids (1 mg corticosterone or 10 microgram dexamethasone) stimulated activity to a level 25-50% higher than that in sham-operated rats. Polyribosome aggregation, as measured by sucrose density gradient analysis, was also greater in treated hypophysectomized rats than in sham-operated rats. On the other hand, a daily sc dose of 100 microgram of the noncorticotropic fragment, ACTH-(1-10), did not stimulate brain polyribosome activity in hypophysectomized rats but merely restored it to the level observed in sham-operated rats. The present study suggests that stimulation of cerebral protein synthesis by ACTH and corticotropic ACTH analogs may be partly due to their ability to promote adrenal steroid secretion. Their stimulatory effect and that of glucocorticoids might explain their physiological roles during stress and learning.

Adrenocorticotropin analogs and glucocorticoids in the hypophysectomized rat. I. Effects on liver polyribosomes and rough endoplasmic reticulum

Hypophysectomy decreased polyribosome aggregation and activity in rat liver. Polyribosome aggregation was measured by sucrose density gradient analysis and polyribosome activity was determined by the incorporation of labeled amino acids into protein in a cell-free system using pH 5 enzymes from sham-operated rats. Hypophysectomy also totally disorganized the rough endoplasmic reticulum of hepatocytes, as shown by electron micrographs. The sc administration of the ACTH fragments, Hoe 433 (corticotropic) and Org 2766 (noncorticotropic), and of glucocorticoids (dexamethasone or corticosterone) to hypophysectomized rats restored these parameters to the levels recorded in sham-operated rats in a dose-dependent fashion 5 h after injection; the effects were maintained until at least 24 h. The sc administration of the noncorticotropic but metabolically less stable fragment, ACTH-(1-10), had only a partial effect. The potency of a noncorticotropic ACTH fragment (Org 2766) in hypophysectomized rats suggests that ACTH may act on liver protein synthesis without the intervention of glucocorticoids or pituitary hormones.

[Molecular basis for the use of steroids in psychiatry (author's transl)]

In animals, estrogens and progestins modulate food intake, running wheel activity and sexual behavior, androgens stimulate sexual behavior and aggression, and corticoids influence cerebral electrolyte regulation, sleep and memory. In this and other studies, we have established that soluble receptors binding steroid hormones are present, often in high concentration, in various central structures such as hypothalamus, cortex, hippocampus and amygdala and have shown that some of the effects of steroids on behavior can be related to their interaction with these receptors and the resultant biochemical events. Thus, in the rat, the induction of sexual behavior by estrogens and progesterone can be related to the increase in progestin receptor induced in the hypothalamus by estrogens. The action of glucocorticoids has been implicated in memory processes involving protein synthesis and this study shows that glucocorticoids stimulate protein synthesis in the cortex of hypophysectomized rats, a structure rich in glucocorticoid receptors. Since the hormonal specificity of receptor binding is similar in peripheral and central target tissues, it is suggested that competition experiments on a peripheral target tissue can be used as a simple test to select compounds (agonists or antagonists) able to replace endogenous hormones at the receptor site in the treatment of psychiatric disorders due to endocrine dysfunction (hormone deficit or excess).

Detection and localization of 14-3-2 protein in primary cultures of embryonic rat brain

The development of embryonic rat brain in cell cultures was studied by an immunocytochemical method based on the detection of 14-3-2 protein (neuron-specific enolase or NSE), a neuron-specific protein. This protein was already present in undifferentiated neurons (less than 5 days in culture), being dispersed throughout the cytoplasm, though seemingly concentrated in the vicinity of polyribosomal structures. It was not found in nuclei, in mitochondria or in the Golgi apparatus. During neuron differentiation, the location of 14-3-2 protein was related to neurite development insofar as it was detected along the axon and even in what could be taken to be the presynaptic region of numerous interneuron contacts. In contact areas, a thickening of the junction membrane was observed but the presence of 14-3-2 protein was always unilateral demonstrating the absence of a true synapse and reflecting the halt in neurite development observed after 15 days in culture. The presence of 14-3-2 protein in the cell cultures was confirmed by a microcomplement fixation assay. The protein detected in cell cultures had the same immunological properties as that found in the 17-day-old embryo, but was slightly different from that found in adult rat brain. This observation can be confronted with the lack of neuron maturation in the immunocytochemical studies.

Stability of 70S ribosomes in relation to misreading and antibacterial activity of aminoglycosides

The anomeric aminoglycosides, RU 21886 and RU 23468, which both have a 2-deoxystreptamine residue, stabilize 70S ribosomes to similar extents at low magnesium ion concentrations. Only RU 21886, however, has marked antibacterial and bactericidal activity and gives rise to a high level of misreading in cell-free protein synthesizing systems. It would thus appear that the ability to stabilize the association of the two ribosomal subunits does not necessarily lead to errors in translation.

Paromomycin and dihydrostreptomycin binding to Escherichia coli ribosomes

Paromomycin binds specifically to a single type of binding site on the 70-S streptomycin-sensitive Escherichia coli ribosome. This site is different from that of dihydrostreptomycin since paromomycin binds to streptomycin-resistant ribosomes and sine dihydrostreptomycin does not compete for paromomycin binding. Paromomycin binding, unlike dihydrostreptomycin binding, is independent of changes in ribosome concentration but influenced by magnesium ion concentration. Moreover, paromomycin does not bind to the 30-S subunit of the streptomycin-sensitive ribosome, except in the presence of dihydrostreptomycin, which probably induces the conformational changes necessary for a paromomycin binding site. This induction does not occur with streptomycin-resistant ribosomes. Neither antibiotic binds to the 50-S subunit. In general, binding of the one antibiotic increases the number of sites available for binding of the other. Both antibiotics exhibit marked non-specific binding at high antibiotic/ribosome ratios. Competition studies have enabled the classification of other aminoglycosides according to their ability to compete for the paromomycin and dihydrostreptomycin binding sites. Derivatives structurally related to paromomycin compete for its binding, the degree of competition being related to antibacterial activity, but do not compete for dihydrostreptomycin binding; they, on the contrary, increase the number of dihydrostreptomycin binding sites. Neither gentamicin nor kanamycin derivatives, which induce a high level of misreading, nor kasugamycin and spectinomycin, which do not induce misreading, compete for paromomycin or dihydrostreptomycin binding sites. Other sites may be involved in the binding of these aminoglycosides and in inducing misreading.

Infectious DNA from herpes simplex virus: infectivity of double-stranded and single-stranded molecules

The infectious units in native and alkalidenatured preparations of DNA of herpes simplex virus were characterized with respect to their sensitivity to Neurospora crassa endonuclease, their sedimentation properties in high-salt, neutral sucrose gradients, and their sensitivity to hydrodynamic shearing forces. Infectious molecules in native preparations were resistant to N. crassa endonuclease, sedimented at 56 S, and were highly sensitive to shearing forces. After alkaline denaturation, infectious molecules became sensitive to the N. crassa enzyme, sedimented at 200 S, and were relatively resistant to shear. We conclude that both intact duplex molecules ([unk]100 x 10(6) daltons) and intact single strands ([unk]50 x 10(6) daltons) are capable of initiating productive infection.