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At least 829 records · Page 46Linked to original sources
PubMed1997

Antisense oligonucleotides in neuroendocrinology: enthusiasm and frustration.

Antisense oligodeoxynucleotides (ODN) offer the potential advantage to manipulate neuropeptide or neuropeptide receptor expression within the brain transiently and site-specifically, thus providing a tool for neuroendocrinological research into the physiological function of a particular neuropeptide system. In this study, various approaches are introduced which reveal that antisense ODN may exert acute, short-term effects on neuronal responsiveness to afferent stimuli, as well as long-term effects on neuropeptide/receptor protein availability in a given system depending on the duration of treatment. Short-term effects were seen in that oxytocin (OXT) and vasopressin (AVP) antisense ODN affected electrophysiological and secretory parameters of oxytocinergic and vasopressinergic neurons, respectively, as well as their ability to express the Fos protein in response to afferent stimulation a few hours after a single infusion into the hypothalamic supraoptic nucleus. In this study, two methodological approaches to study long-term effects of the antisense ODN are exemplified, in which antisense ODN directed against the mRNA coding for the neuropeptide itself or its receptor were used. The repeated infusion of corticotropin releasing hormone (CRH) antisense ODN into the paraventricular nucleus resulted in reduced immunoreactive CRH, but not AVP, in the external zone of the median eminence. Furthermore, in order to evaluate the receptor-mediated effects of CRH and AVP released locally within the paraventricular nucleus on adrenocorticotropin (ACTH) release from the pituitary, CRH receptor (and also AVP receptor) antisense ODN were repeatedly infused into the hypothalamic nuclei; this treatment resulted in an elevation of stimulated, but not basal, ACTH release into the blood. However, in addition to these obvious antisense effects, results are discussed which demonstrate sequence-unspecific effects of phosphorothioated ODN, suggesting that some of their mechanisms of action are not yet understood.

Animals↗
PubMed1998

Battey's operation: an exercise in surgical frustration.

Robert Battey (1828-1895) introduced bilateral oophorectomy for the treatment of non-ovarian conditions in 1872, coining the term "normal ovariotomy" for the operation. Normal ovariotomy - a contradictio in terminis - was practised widely for several decades. Alfred Hegar (1830-1914), among many other gynaecologists, extended the indications of Battey's operation to include the treatment of various ovarian conditions as well, e.g., small tumors. Better insight into female physiology and ovarian function finally pushed the sinister operation of Robert Battey from the scene.

Female↗
PubMed2002

Cyclic trinuclear and chain of cyclic trinuclear copper(II) complexes containing a pyramidal Cu(3)O(H) core. Crystal structures and magnetic properties of [Cu(3)(mu(3)-OH)(aaat)(3)(H(2)O)(3)](NO(3))(2).H(2)O [aaat = 3-acetylamino-5-amino-1,2,4-triazolate] and ([Cu(3)(mu(3)-OH)(aat)(3)(mu(3)-SO(4))].6H(2)O)(n) [aat = 3-acetylamino-1,2,4-triazolate]: new cases of spin-frustrated systems.

New copper(II) complexes of the cyclic trinuclear type with 1,2,4-triazole ligands, [Cu(3)(mu(3)-OH)(aaat)(3)(H(2)O)(3)](NO(3))(2).H(2)O [Haaat = 3-acetylamino-5-amino-1,2,4-triazole] (1) and ([Cu(3)(mu(3)-OH)(aat)(3)(mu(3)-SO(4))].6H(2)O)(n) [Haat = 3-acetylamino-1,2,4-triazole] (2), have been prepared and characterized by X-ray crystallography and magnetic measurements. Compound 1, the first reported with the ligand (H)aaat, consists of discrete trinuclear cations, associated NO(3)(-) anions and lattice water molecules. Compound 2 consists of unusual chains of trinuclear units with a tridentate sulfato group linking the trimeric units and water molecules stabilizing the crystal lattice. In both complexes, 1 and 2, the trinuclear [Cu(3)(OH)L(3)] unit contains a pyramidal Cu(3)-mu(3)OH core, and an almost flat Cu(3)N(6) ring formed by the N,N-bridging triazolato groups. The Cu...Cu' intratrimeric distances are 3.35-3.37-3.39 A in 1 and 3.34-3.34-3.36 A in 2. The copper atoms are five-coordinated with a distorted square-pyramidal geometry. Magnetic measurements have been performed in the 1.9-300 K temperature range. In the high-temperature region (T > 90 K), experimental data could be satisfactorily reproduced by using an isotropic exchange model, H = -J(S(1)S(2) + S(2)S(3) + S(1)S(3)), with J = -194.6 cm(-1) and g = 2.08 for 1, and J = -185.1 cm(-1) and g = 2.10 for 2. The magnitude of the antiferromagnetic exchange in both complexes is discussed on the basis of their structural features by comparison with reported N,N-pheripherically bridged trinuclear systems. In order to fit the experimental magnetic data at low temperature, an antisymmetric exchange term, H(AS) = G(S(1)xS(2) + S(2)xS(3) + S(1)xS(3)), had to be introduced, with G = 27.8 (1) and 31.0 (2) cm(-1). Crystal data: C(12)H(27)Cu(3)N(17)O(14) (1) (MW = 824.13) crystallizes in the triclinic space group, P(-)1, Z = 2, with the cell dimensions a = 8.852(2) A, b = 11.491(3) A, c = 15.404(3) A, alpha = 70.43(3) degrees, beta = 75.11(2) degrees, gamma = 88.43(2) degrees, and V = 1423.8(5) A(3), D(calcd) = 1.922 g cm(-)(3); the final agreement values were R1 = 0.0822 and wR2 = 0.2300 for 4989 unique reflections. C(12)H(28)Cu(3)N(12)O(14)S (2) (MW = 787.14) crystallizes in the triclinic space group, P(-)1, Z = 2, with the cell dimensions a = 7.146(6) A, b = 14.26(1) A, c = 15.35(2) A, alpha = 109.0(9) degrees, beta = 93.6(9) degrees, gamma = 99.5(7) degrees, and V = 1448(2) A(3), D(calcd) = 1.806 g cm(-3); the final agreement values were R1 = 0.0628 and wR2 = 0.1571 for 3997 "observed" reflections.

Journal Article↗
PubMed2006

Metal-metal bonding in sterically frustrated dipalladium species.

Stoichiometric-deficient lithiation of (2,6-diisopropylphenyl)(4-methylpyridin-2-yl)amine and reaction with [(cod)PdCl2] (cod = 1,5-cyclooctadiene) yield a dimeric Pd complex. X-ray structural analysis of this complex reveals a very short Pd-Pd distance (2.429 A). Topological analysis of the electron density and the electron localization function from scalar relativistic density functional theory calculations clearly indicate a Pd(I)-Pd(I) sigma-bonding interaction, for which the corresponding occupied localized orbital can be identified.

Journal Article↗
PubMed2004

Frustrated beta-chloride elimination. Selective arene alkylation by alpha-chloronorbornene catalyzed by electrophilic metallocenium ion pairs.

Single-site polymerization catalysts generated in situ via activation of Cp*MMe(3) (Cp* = C(5)Me(5); M = Ti, Zr), (CGC)MMe(2) (CGC = C(5)Me(4)SiMe(2)NBu(t)(); M = Ti, Zr), and Cp(2)ZrMe(2) with Ph(3)C(+)B(C(6)F(5))(4)(-) catalyze alkylation of aromatic molecules (benzene, toluene) with alpha-chloronorbornene at room temperature, to regioselectively afford the 1:1 addition products exo-1-chloro-2-arylnorbornane (aryl = C(6)H(5) (1a), C(6)H(4)CH(3) (1b)) in good yields. Analogous deuterium-labeled products exo-1-chloro-2-aryl-d(n)-norbornane-7-d(1) (aryl-d(n) = C(6)D(5) (1a-d(6)), C(6)D(4)CD(3) (1b-d(8))) are obtained via catalytic arylation of alpha-chloronorbornene in either benzene-d(6) or toluene-d(8). Isolated ion-pair complexes such as (CGC)ZrMe(toluene)(+)B(C(6)F(5))(4)(-) and Cp(2)ThMe(+)B(C(6)F(5))(4)(-) also catalyze the reaction of alpha-chloronorbornene in toluene-d(8) to give 1b-d(8) in good yields, respectively. Small quantities of the corresponding bis(1-chloronorbornyl)aromatics 2 are also obtained from preparative-scale reactions. These reactions exhibit turnover frequencies exceeding 120 h(-1) (for the Cp*TiMe(3)/Ph(3)C(+)B(C(6)F(5))(4)(-)-catalyzed system), and chlorine-free products are not observed. Compounds 1 and 2 were characterized by (1)H, (2)H, (13)C, and 2D NMR, GC-MS, and elemental analysis. The aryl group exo-stereochemistry in 1a and 1b is established using (1)H-(1)H COSY, (1)H-(13)C HMBC, and (1)H-(1)H NOESY NMR, and is further corroborated by X-ray analysis of the product 1,4-bis(exo-1-chloro-2-norbornyl)benzene (2a). Control experiments and reactivity studies on each component step suggest a mechanism involving participitation of the metal electrophiles in the catalytic cycle.

Journal Article↗
PubMed1988

Impact frustration of the origin of life.

One possible definition for the origin of life on Earth is the time at which the interval between devastating environmental insults by impact exceeded the timescale for establishing self-replicating proto-organisms. A quantitative relationship for the Hadean (pre-3,800 Myr ago) and Early Archean (3,800 to 3,400 Myr) impact flux can be derived from the lunar and terrestrial impact records. Also, the effects of impact-related processes on the various environments proposed for abiogenesis (the development of life through chemical evolution from inorganic materials) can be estimated. Using a range of plausible values for the timescale for abiogenesis, the interval in time when life might first have bootstrapped itself into existence can be found for each environment. We find that if the deep marine hydrothermal setting provided a suitable site, abiogenesis could have happened as early as 4,000 to 4,200 Myr ago, whereas at the surface of the Earth abiogenesis could have occurred between 3,700 and 4,000 Myr.

Earth, Planet↗