A redox system for brain targeted estrogen delivery causes chronic body weight decrease in rats

The effects of 2 redox based carriers for brain directed delivery of estradiol (CDS-E2) and ethinyl estradiol (CDS-EE) on body weight were examined in rats. A single dose of CDS-E2 (3 mg/kg) decreased weight gain in castrate rats for at least 24 days. The dose response of weight gain and LH suppression were compared 12 days and 12 to 25 after CDS-E2 and CDS-EE, respectively, in ovariectomized (OVX) rats. Weight decrease was detected at a lower dose and was significant for longer after drug treatment than LH decrease. Both compounds were more potent than equimolar estradiol or estradiol valerate in reducing weight gain. Intact rats also showed decreased weight gain but were less sensitive to CDS-E2 compared to OVX rats. The effects appeared to be estrogen specific as carrier-linked testosterone had no effect on weight. The mechanisms of sustained and potent drug effects on weight are being explored.     

Nitrogen Oxyanion-dependent Dissociation of a Two-component Complex That Regulates Bacterial Nitrate Assimilation

Nitrogen is an essential nutrient for growth and is readily available to microbes in many environments in the form of ammonium and nitrate. Both ions are of environmental significance due to sustained use of inorganic fertilizers on agricultural soils. Diverse species of bacteria that have an assimilatory nitrate/nitrite reductase system (NAS) can use nitrate or nitrite as the sole nitrogen source for growth when ammonium is limited. In Paracoccus denitrificans, the pathway-specific two-component regulator for NAS expression is encoded by the nasT and nasS genes. Here, we show that the putative RNA-binding protein NasT is a positive regulator essential for expression of the nas gene cluster (i.e. nasABGHC). By contrast, a nitrogen oxyanion-binding sensor (NasS) is required for nitrate/nitrite-responsive control of nas gene expression. The NasS and NasT proteins co-purify as a stable heterotetrameric regulatory complex, NasS-NasT. This protein-protein interaction is sensitive to nitrate and nitrite, which cause dissociation of the NasS-NasT complex into monomeric NasS and an oligomeric form of NasT. NasT has been shown to bind the leader RNA for nasA. Thus, upon liberation from the complex, the positive regulator NasT is free to up-regulate nas gene expression.     

Experimental Methyl Mercury Neurotoxicity: Locus of Mercurial Inhibition of Brain Protein Synthesis In Vivo and In Vitro

Brain cell-free protein synthesis is inhibited by methyl mercury chloride (MeHg) following in vivo or in vitro administration. In this report, we have identified the locus of mercurial inhibition of translation. Intraperitoneal injection of MeHg (40 nmol/g body wt) induced variable inhibition of amino acid incorporation into the post-mitochondrial supernatant (PMS) harvested from the brain of young (10-20-day-old) rats. No mercurial-induced disaggregation of brain polyribosomes nor change in the proportion of 80S monoribosomes was detected on sucrose density gradients. No difference in total RNA was found in the PMS. Initiation complex formation was stimulated by MeHg, as detected by radiolabelled methionine binding to 80S monoribosomes following continuous sucrose density gradient centrifugation. After micrococcal nuclease digestion of endogenous mRNA, both in vivo and in vitro MeHg inhibited polyuridylic acid-directed incorporation of [3H]phenylalanine. However, the in vivo inhibition was no longer observed when [3H]phenylalanyl-tRNAPhe replaced free [3H]phenylalanine in the incorporation assay. The formation of peptidyl[3H]puromycin revealed no difference from controls. There was significant mercurial inhibition of phenylalanyl-tRNA Phe synthetase activity in pH 5 enzyme fractions derived from brain PMS of MeHg-poisoned rats. These experiments revealed that the apparent MeHg inhibition of brain translation in vivo and in vitro is due primarily to perturbation in the aminoacylation of tRNA and is not associated with defective initiation, elongation, or ribosomal function.     

Fluorimetric determination of d-amino acid oxidase

1. A sensitive fluorimetric procedure for the assay of d-amino acid oxidase has been developed. 2. The method depends on the formation of a fluorescent derivative, 2-hydroxy-3-methylquinoxaline, on condensation of pyruvate with o-phenylenediamine in acid medium. 3. 2-Hydroxy-3-methylquinoxaline fluoresces strongly in 50% (v/v) sulphuric acid after excitation at 375mmu. A single emission peak is observed at 480mmu. 4. Formation of the quinoxaline is dependent on time, temperature, acidity and relative concentration of reactants. 5. A particulate preparation from mouse kidney required FAD for optimum activity at pH8.5; K(m) was 3.8x10(-3)m; K(FAD) was 1.4x10(-7)m and the reaction was strongly inhibited by p-chloromercuribenzoate and phenylmercuric acetate. 6. Subcellular fractionation on a sucrose density gradient confirmed that the d-amino acid oxidase was localized on small granules.     

Somatostatin gene expression in the thymus gland

A complex pattern of interactions appears to exist between the immune and neuroendocrine systems. Recently, vasopressin, oxytocin and vasoactive intestinal peptide have been isolated from the thymus. Using a rat somatostatin antisense RNA probe we have demonstrated expression of the somatostatin gene in the rat thymus. Furthermore, we have shown that the levels of thymic somatostatin mRNA exhibit a bell-shaped response to dexamethasone administration. Lipocortin I and II antisense RNA probes have been used as a positive control for the effects of the dexamethasone. We would suggest that somatostatin acts in the thymus in a paracrine mode to modulate T lymphocyte development.     

Antigenic specificity of antibody-dependent cell-mediated cytotoxicity directed against human immunodeficiency virus in antibody-positive sera.

Antibody-dependent cell-mediated cytotoxicity (ADCC) specific for human immunodeficiency virus (HIV) has been described for HIV-infected individuals. To determine the antigenic specificity of this immune response and to define its relationship to the disease state, an ADCC assay was developed using Epstein-Barr virus-transformed lymphoblastoid cell line targets infected with vaccinia virus vectors expressing HIV proteins. The vaccinia virus vectors induced appropriate HIV proteins (envelope glycoproteins gp160, gp120, and gp41 or gag proteins p55, p40, p24, and p17) in infected lymphoblastoid cell lines as demonstrated by radioimmunoprecipitation and syncytia formation with c8166 cells. Killer cell-mediated, HIV-specific ADCC was found in sera from HIV-seropositive but not HIV-seronegative hemophiliacs. This HIV-specific response was directed against envelope glycoprotein but was completely absent against target cells expressing the HIV gag proteins. The ADCC directed against gp160 was present at serum dilutions up to 1/316,000. There was no correlation between serum ADCC titer and the stage of HIV-related illness as determined by T-helper-cell numbers. These experiments clearly implicated gp160 as the target antigen of HIV-specific ADCC activity following natural infection. Vaccines which stimulate antibodies directed against gp160, which are capable of mediating ADCC against infected cells, could be important for protection against infection by cell-associated virus.     

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) reduces lipoprotein lipase activity in the adipose tissue of the guinea pig

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) administered to young male guinea pigs at a dose of 1 microgram/kg (single intraperitoneal injection) caused a large reduction in adipose tissue lipoprotein lipase (LPL) activity. This effect occurred rapidly; a 70% decrease was noticed after 24 hour and 80% of LPL activity was lost by 48 hours when the serum triglyceride levels increased to 175% of control levels. LPL is known to play an important role in controlling the amount of free fatty acids supplied to adipose tissues. Administration of a large dose of glucose to fasted guinea pigs, which have shown a similar weight loss, but less LPL loss than TCDD-treated animals, had the effect of elevating their adipose LPL levels back to a near normal level, whereas the same treatment caused no significant increase in the LPL levels of TCDD-treated animals. Evidence indicates that the TCDD-caused decline in LPL activity is irreversible. As a consequence, the affected guinea pigs are incapable of responding to changes in nutritional status.     

Failure of atractyloside to inhibit synaptosomal mitochondrial energy transduction

Studies on synaptosome mitochondrial respiration are complicated by “free” mitochondria. Veratridine stimulation of synaptosomal respiration was due to increased Na⁺ cycling at the synaptosome membrane associated with increased oxidative phosphorylation of intraterminal ADP and was inhibited by oligomycin, ouabain or Na⁺ free medium. Atractylate or carboxyatractyloside failed to block veratridine-stimulated respiration but inhibited exogenous-ADP-stimulated respiration. Protein synthesis in the synaptosome fraction was inhibited by oligomycin, valinomycin or 2,4-dinitrophenol but was unaffected by excess atractylate. No change in synaptosomal adenine nucleotide content was found in the presence of atractylate, although a significant decrease in the [ATP]/[ADP] was found with oligomycin, veratridine or valinomycin. These findings show that atractylate does not modify intraterminal mitochondrial energy transduction and indirectly suggest an impermeability of the synaptosome membrane to atractylate.