Prevention of pathological change and cognitive degeneration of Tg2576 mice by inoculating Aβ1–15 vaccine

This study aims to discuss the effect of preventing pathological changes and cognitive degeneration of Tg2576 mice by inoculating the subunit fragment of Aβ vaccine. Thirty-two Tg2576 mice were randomly divided into four groups, each having eight mice: Group I, the control group, inoculated with adjuvants; Group II, the Aβ42 group, inoculated with Aβ^₄₂ vaccine; Group III, the Aβ_1―15 group, inoculated with Aβ_1―15 vaccine; and Group IV, the Aβ_36―42 group, inoculated with Aβ_36―42 vaccine. The titer of the serum anti-body against Aβ₄₂ (Group II) was significantly higher than that of the control group (Group I), and a low level of antibodies could be detected in the brain homogenate in the three vaccine-inoculated groups. Morris water maze test showed that the Aβ42 group, Aβ_1―15 group and Aβ_36―42 group were obviously im-proved compared with the control group. The cultured splenocytes sampled from each group were induced by Con A or their respective antigens, and the cell proliferation of the three vaccine-inoculated groups was significantly higher than that of the control group. In the Aβ₄₂ group, IL2 and IFN-γ were relatively low and IL4 and IL10 were relatively high. By contrast, IL4 and IL10 were much higher in the Aβ_1―15 group and IL2 and IFN-γ were much higher in the Aβ_36―42 group. The immunohistochemical test showed a large number of senile plaques in the brain cortex and hippocampus of the mice in the con-trol group, no senile plaque in the brain of the Aβ_1―15 group and Aβ₄₂ group mice, and a small number of senile plaques in the brain of the Aβ_36―42 group mice. The results suggest that the subunit fragment of Aβ_1―15 vaccine could prevent not only cognitive and behavioral degeneration but also Aβ deposition and formation of senile plaques in Tg2576 mice.     

Prevention of pathological change and cognitive degeneration of Tg2576 mice by inoculating Aβ_(1-15) vaccine

This study aims to discuss the effect of preventing pathological changes and cognitive degeneration of Tg2576 mice by inoculating the subunit fragment of Aβ vaccine. Thirty-two Tg2576 mice were randomly divided into four groups, each having eight mice: Group I, the control group, inoculated with adjuvants; Group II, the Aβ42 group, inoculated with Aβ42 vaccine; Group III, the Aβ1―15 group, inoculated with Aβ1―15 vaccine; and Group IV, the Aβ36―42 group, inoculated with Aβ36―42 vaccine. The titer of the serum anti-body against Aβ42 (Group II) was significantly higher than that of the control group (Group I), and a low level of antibodies could be detected in the brain homogenate in the three vaccine-inoculated groups. Morris water maze test showed that the Aβ42 group, Aβ1―15 group and Aβ36―42 group were obviously im-proved compared with the control group. The cultured splenocytes sampled from each group were induced by Con A or their respective antigens, and the cell proliferation of the three vaccine-inoculated groups was significantly higher than that of the control group. In the Aβ42 group, IL2 and IFN-γ were relatively low and IL4 and IL10 were relatively high. By contrast, IL4 and IL10 were much higher in the Aβ1―15 group and IL2 and IFN-γ were much higher in the Aβ36―42 group. The immunohistochemical test showed a large number of senile plaques in the brain cortex and hippocampus of the mice in the con-trol group, no senile plaque in the brain of the Aβ1―15 group and Aβ42 group mice, and a small number of senile plaques in the brain of the Aβ36―42 group mice. The results suggest that the subunit fragment of Aβ1―15 vaccine could prevent not only cognitive and behavioral degeneration but also Aβ deposition and formation of senile plaques in Tg2576 mice.     

The neural γ<Subscript>2</Subscript>α<Subscript>1</Subscript>β<Subscript>2</Subscript>α<Subscript>1</Subscript>β<Subscript>2</Subscript> gamma amino butyric acid ion channel receptor: structural analysis of the effects of the ivermectin molecule and disulfide bridges

While ~30% of the human genome encodes membrane proteins, only a handful of structures of membrane proteins have been resolved to high resolution. Here, we studied the structure of a member of the Cys-loop ligand gated ion channel protein superfamily of receptors, human type A γ₂α₁β₂α₁β₂ gamma amino butyric acid receptor complex in a lipid bilayer environment. Studying the correlation between the structure and function of the gamma amino butyric acid receptor may enhance our understanding of the molecular basis of ion channel dysfunctions linked with epilepsy, ataxia, migraine, schizophrenia and other neurodegenerative diseases. The structure of human γ₂α₁β₂α₁β₂ has been modeled based on the X-ray structure of the Caenorhabditis elegans glutamate-gated chloride channel via homology modeling. The template provided the first inhibitory channel structure for the Cys-loop superfamily of ligand-gated ion channels. The only available template structure before this glutamate-gated chloride channel was a cation selective channel which had very low sequence identity with gamma aminobutyric acid receptor. Here, our aim was to study the effect of structural corrections originating from modeling on a more reliable template structure. The homology model was analyzed for structural properties via a 100 ns molecular dynamics (MD) study. Due to the structural shifts and the removal of an open channel potentiator molecule, ivermectin, from the template structure, helical packing changes were observed in the transmembrane segment. Namely removal of ivermectin molecule caused a closure around the Leu 9 position along the ion channel. In terms of the structural shifts, there are three potential disulfide bridges between the M1 and M3 helices of the γ₂ and 2 α₁ subunits in the model. The effect of these disulfide bridges was investigated via monitoring the differences in root mean square fluctuations (RMSF) of individual amino acids and principal component analysis of the MD trajectory of the two homology models—one with the disulfide bridge and one with protonated Cys residues. In all subunit types, RMSF of the transmembrane domain helices are reduced in the presence of disulfide bridges. Additionally, loop A, loop F and loop C fluctuations were affected in the extracellular domain. In cross-correlation analysis of the trajectory, the two model structures displayed different coupling in between the M2–M3 linker region, protruding from the membrane, and the β1-β2/D loop and cys-loop regions in the extracellular domain. Correlations of the C loop, which collapses directly over the bound ligand molecule, were also affected by differences in the packing of transmembrane helices. Finally, more localized correlations were observed in the transmembrane helices when disulfide bridges were present in the model. The differences observed in this study suggest that dynamic coupling at the interface of extracellular and ion channel domains differs from the coupling introduced by disulfide bridges in the transmembrane region. We hope that this hypothesis will be tested experimentally in the near future.     

Functional blockade of α<Subscript>5</Subscript>β<Subscript>1</Subscript> integrin induces scattering and genomic landscape remodeling of hepatic progenitor cells

Background  

Cell scattering is a physiological process executed by stem and progenitor cells during embryonic liver development and postnatal organ regeneration. Here, we investigated the genomic events occurring during this process induced by functional blockade of α₅β₁ integrin in liver progenitor cells.     

Comparable Attenuation of Aβ<Subscript>25–35</Subscript>-Induced Neurotoxicity by Quercitrin and 17β-Estradiol in Cultured Rat Hippocampal Neurons

In the present work, potential protective effects of quercitrin (a phytoestrogen) on Aβ-induced neurotoxicity in cultured rat hippocampal neurons were investigated in comparison with 17β-estradiol. Cell viability, oxidative status, and antioxidative potentials were used as comparative parameters. Co-exposure of cultured neurons to Aβ_25–35 with either quercitrin or 17β-estradiol (50–100 μM) for 72 h attenuated Aβ_25–35-induced neurotoxicity and lipid peroxidation, but not Aβ_25–35-induced ROS accumulation. However, only 17β-estradiol counteracted a reduction in glutathione content and only quercitrin counteracted a reduction in glutathione peroxidase activity. Both compounds displayed no effects on superoxide dismutase activity. A specific estrogen receptor antagonist, ICI 182780, did not abolish neuroprotective effects of quercitrin and 17β-estradiol. These findings suggested that quercitrin and 17β-estradiol attenuated Aβ_25–35-induced neurotoxicity in a comparable manner. Underlying neuroprotective mechanisms of both compounds were probably not related to estrogen receptor-mediated genomic mechanisms but might involve with their antioxidant and free radical scavenging properties.     

Effect of the β-amyloid peptide Aβ<Subscript>25–35</Subscript> and fullerene C<Subscript>60</Subscript> on the activity of enzymes in erythrocytes

The effect of the β-amyloid peptide Aβ_25–35 and fullerene C₆₀ on the activity of the cytoplasmic enzymes lactate dehydrogenase (LDH) and glutathione peroxidase (GLP), and membrane-bound phosphofructokinase (PFK) and Na⁺,K⁺-ATPase in human erythrocytes has been studied. When used in combination, the cytotoxins decrease the activity of LDH and PFK in a nonadditive manner; in this case, Aβ_25–35 protects PFK against the inhibitory effect of C₆₀. The activity of LDH, GLP, and PFK decreases within the first 2–20 min of incubation of erythrocytes with Aβ_25–35 in the absence of glucose. The addition of glucose sharply decreases the inhibitory action of Aβ_25–35 on LDH and GLP but does not affect the fourfold decrease in activity of PFK; the activity of membrane-bound Na⁺,K⁺-ATPase does not depend on the presence of glucose. Possible mechanisms of interaction of Aβ_25–35 and fullerene C₆₀ with the erythrocyte membrane and enzymes are discussed.     

Kinetic analysis of recombinant mammalian α<Subscript>1</Subscript> and α<Subscript>1</Subscript>β glycine receptor channels

To analyze the influence of the beta-subunit on the kinetic properties of GlyR channel currents, alpha(1)-subunits and alpha(1)beta-subunits were transiently expressed in HEK 293 cells. A piezo dimorph was used for fast application of glycine to outside-out patches. The rise time of activation was dose dependent for both receptors and decreased with increasing glycine concentrations. Subunit composition had no effect on the time course of activation. Coexpression of alpha(1)- and beta-subunits resulted in a significantly lower EC(50) and a reduced slope of the dose-response curve of glycine compared with expression of alpha(1)-subunits alone. For both receptor subtypes, the time course of desensitization was concentration dependent. Desensitization was best fitted with a single time constant at 10-30 micro M, with two at 0.1 mM, and at saturating concentrations (0.3-3 mM) with three time constants. Desensitization of homomeric alpha(1)-receptor channels was significantly slower than that of alpha(1)beta-receptor channels. The time course of current decay after the end of glycine pulses was tested at different pulse durations of 1 mM glycine. It was best fitted with two time constants for both alpha(1) and alpha(1)beta GlyR channels, and increased significantly with increasing pulse duration.     

Correlated motions of C′–N and C<Subscript>α</Subscript>–C<Subscript>β</Subscript> pairs in protonated and per-deuterated GB3

We investigated correlated µs-ms time scale motions of neighboring ¹³C′–¹⁵N and ¹³C_α–¹³C_β nuclei in both protonated and perdeuterated samples of GB3. The techniques employed, NMR relaxation due to cross-correlated chemical shift modulations, specifically target concerted changes in the isotropic chemical shifts of the two nuclei associated with spatial fluctuations. Field-dependence of the relaxation rates permits identification of the parameters defining the chemical exchange rate constant under the assumption of a two-site exchange. The time scale of motions falls into the intermediate to fast regime (with respect to the chemical shift time scale, 100–400 s^?1 range) for the ¹³C′–¹⁵N pairs and into the slow to intermediate regime for the ¹³C_α–¹³C_β pairs (about 150 s^?1). Comparison of the results obtained for protonated and deuterated GB3 suggests that deuteration has a tendency to reduce these slow scale correlated motions, especially for the ¹³C_α–¹³C_β pairs.     

Co-transformation of <Emphasis Type="Italic">Panax</Emphasis> major ginsenosides Rb<Subscript>1</Subscript> and Rg<Subscript>1</Subscript> to minor ginsenosides C–K and F<Subscript>1</Subscript> by <Emphasis Type="Italic">Cladosporium cladosporioides</Emphasis>

Rb₁ and Rg₁ are the major ginsenosides in protopanaxadiol and protopanaxatriol. Their content in ginsenosides was 23.8 and 17.6%, respectively. A total of 22 isolates of β-glucosidase producing microorganisms were isolated from the soil of a ginseng field using Esculin-R2A agar. Among these isolates, the strain GH21 showed the strongest activities to convert ginsenoside Rb₁ and Rg₁ to minor ginsenosides compound-K and F₁, respectively. Ginsenosides Rb₁ and Rg₁ bioconversion rates were 74.2 and 89.3%, respectively. Meanwhile, the results demonstrated that the ginsenoside Rg₁ could change the biotransformation pathway of ginsenoside Rb₁ by inhibiting the formation of the intermediate metabolite gypenoside-XVII. GH21 was identified as a Cladosporium cladosporioides species based on the internal transcribed spacers (ITS) ITS1-5.8S-ITS2 rRNA gene sequences constructed phylogenetic trees.     

<Superscript>1</Superscript>H, <Superscript>13</Superscript>C,and <Superscript>15</Superscript>N backbone chemical shift assignments of 4E-BP1<Subscript>44–87</Subscript> and 4E-BP1<Subscript>44–87</Subscript> bound to eIF4E

The eukaryotic translational initiation factor 4G (eIF4G) interacts with the cap-binding protein eIF4E through a consensus binding motif, Y(X)₄LΦ (where X is any amino acid and Φ is a hydrophobic residue). 4E binding proteins (4E-BPs), which also contain a Y(X)₄LΦ motif, regulate the eIF4E/eIF4G interaction. The non- or minimally-phosphorylated form of 4E-BP1 binds eIF4E, preventing eIF4E from interacting with eIF4G, thus inhibiting translation initiation. 4EGI-1, a small molecule inhibitor of the eIF4E/eIF4G interaction that is under investigation as a novel anti-cancer drug, has a dual activity; it disrupts the eIF4E/eIF4G interaction and stabilizes the binding of 4E-BP1 to eIF4E. Here, we report the complete backbone NMR resonance assignment of an unliganded 4E-BP1 fragment (4E-BP1_44–87). We also report the near complete backbone assignment of the same fragment in complex to eIF4E/m⁷GTP (excluding the assignment of the last C-terminus residue, D87). The chemical shift data constitute a prerequisite to understanding the mechanism of action of translation initiation inhibitors, including 4EGI-1, that modulate the eIF4E/4E-BP1 interaction.     

Effects of activation of μ-, κ<Subscript>1</Subscript>-, δ<Subscript>1</Subscript>-, δ<Subscript>2</Subscript>-, and ORL<Subscript>1</Subscript>-receptors on heart resistance to the pathogenic action of delayed ischemia and reperfusion

Different subtypes of opioid receptors (OR) were activated in rats in vivo to study the activation effect on the heart’s resistance to ischemia and reperfusion. It has been established that administration of deltorphin II, a selective δ₂-OR agonist, lowered the infarct size/area at risk index (IS/AAR) by 23%. Naltrexone, naloxone methiodide (an OR inhibitor not penetrating the blood-brain barrier (BBB)), and naltriben (δ₂-antagonist) eliminated the cardioprotective effect of deltorphin II, while BNTX (a δ₁-antagonist) produced no effect on the cardioprotective action of the δ₂-agonist. The infarct-reducing effect of deltorphin II was eliminated by administration of chelerythrine (a protein kinase C (PKC) inhibitor), glibenclamide (a K_ATP-channels inhibitor), and 5-hydroxydecanoate (a mitochondrial K_ATP-channel blocker). Administration of other opioids did not reduce the IS/AAR index. It has been established that all the deltorphins manifest antiarrhythmic potency. Other opioids do not produce any effect on the incidence of arrhythmia occurrences. The antiarrhythmic effect of deltorphin II was eliminated by preliminary administration of naltrexone, naloxone methiodide, and naltriben, but BNTX did not affect the δ₂-agonist’s anti-arrhythmic effect. The preliminary administration of chelerythrine, a PKC inhibitor, eliminated the δ₂ agonist’s antiarrhythmic action. However, glibenclamide and 5-hydroxydecanoate did not alter the antiarrhythmic effect by deltorphin II. Therefore, activation of the peripheral δ₂-ORs reduces the infarct size and prevents the onset of arrhythmias. The antiarrhythmic effect of the δ₂-OR stimulation is mediated by activating PKC and opening the mitochondrial K_ATP-channels. PKC participates in the antiarrhythmic effect of the δ₂-OR activation, but this effect does not depend on the condition of K_ATP-channels.     

Amentoflavone Ameliorates Aβ<Subscript>1–42</Subscript>-Induced Memory Deficits and Oxidative Stress in Cellular and Rat Model

Alzheimer’s disease (AD), a progressive neurodegenerative disease of the central nervous system, is the most common cause of senile dementia. This study aimed to investigate whether amentoflavone (AF), a biflavonoid compound, could exert neuroprotective activities against AD. The AD model was established by the intracranial injection of amyloid-beta (Aβ) in rat models. The effect of AF on cognitive function was examined using the Morris water maze test. Cell survival and apoptosis in the hippocampal region in an animal model were detected using Nissl staining and a terminal deoxynucleotidyl transferased UTP nick-end labeling assay, respectively. The levels of oxidant enzymes were determined by enzyme-linked immunosorbent assay. Signaling molecule expressions were examined by western blotting. Our results showed that AF significantly attenuated Aβ-induced deficits in neurological functions as well as neuronal cell death and apoptosis in the hippocampal region. Moreover, our findings revealed that AF increased nuclear factor erythroid 2-related factor 2 (Nrf2) expression and translocation and activated AMP-activated protein kinase (AMPK) signaling. In a cellular model of AD established by exposing PC12 cells to Aβ, our results provided further evidence that the neuroprotective activities of AF were mediated by modulating Nrf2 through AMPK/glycogen synthase kinase 3 beta signaling. AF exerts a protective effect against Aβ_1–42-induced neurotoxcicity by inducing Nrf2 antioxidant pathways via AMPK signaling activation, which provided experimental evidence that AF might provide a clinical benefit to patients with AD.     

Diazoxide Reverses the Enhanced Expression of K<Subscript>ATP</Subscript> Subunits in Cholinergic Neurons Caused by Exposure to Aβ<Subscript>1-42</Subscript>

The ATP-sensitive potassium channel (K_ATP) play a crucial role in coupling metabolic energy to the cell membrane potential, β-amyloid peptide (Aβ) neurotoxicity has been associated with cellular oxidative stress and metabolic impairment. Whether there is an interaction between K_ATP and Aβ or not? The expression of K_ATP subunits was to be investigated after the cultured primary rat basal forebrain cholinergic neurons being exposed to Aβ_1-42. The subunits of K_ATP: Kir6.1, Kir6.2, SUR1 and SUR2 expressing change was observed by double Immunofluorescence and immunoblotting in cultured cholinergic neurons from different groups: treatment with Aβ_1-42 (group Aβ_1-42), pretreatment with diazoxide and then exposure to Aβ_1-42 (group diazoxide + Aβ_1-42), and the control (group control). The results showed that in response to the treatment with Aβ_1-42 (2 μmol/L) for 24 h, the expression of Kir6.1 and SUR2 were significantly up-regulated, while this change can be partly reversed by pretreatment with diazoxide (1 mmol/L) for 1 h. There were significant increases in all K_ATP subunits expression levels after exposure to Aβ_1-42 for 72 h. However, the up-regulation of Kir6.1, Kir6.2 and SUR2 except SUR1 can be partly reversed by pretreatment with diazoxide (1 mmol/L) for 1 h. It is concluded that exposure to Aβ_1-42 for different time (24 and 72 h) induced differential regulation of K_ATP subunits expression in cultured primary rat basal forebrain cholinergic neurons. The change in composition of K_ATP may contribute to the dysfunction of K_ATP and membrane excitability disturbance. The effect of diazoxide on K_ATP subunits expression may explain, in part, the resistance of diazoxide to the toxicity of Aβ_1-42.     

Comparative characteristics of binding kinetics of specific antagonists by α<Subscript>1</Subscript>- and α<Subscript>2</Subscript>-adrenoceptors in rat cerebral cortex membranes

The binding of specific nonselective α₁- and α₂-adrenoceptor antagonists [³H]prazosine and [³H]RX821002 has been studied on rat cerebral cortex synaptosomal membranes. It is shown that for α₁-adrenoceptors the ligand-receptor interaction corresponds to the model assuming the presence of one pool of receptors and binding of two ligand molecules to the receptor. The parameters of [³H]prazosine binding to α₁-adrenoceptors were: K _d= 1.56 ± 0.17 nM, B _max = 30.25 ± 1.78 fmol/mg protein, n = 2. The parameters of [³H]RX821002 binding to α₂-adrenoceptors were: K _d = 1.94 ± 0.08 nM, B _max = 12.77 ± 3.17 fmol/mg protein, n = 2. For α₂ -adrenoceptors the ligand-receptor interaction corresponded to the same model. For α₁ - and α₂-adrenoceptor antagonists the dissociation constants (K _d) are approximately equal (1.56 ± 0.17 and 1.94 ± 0.08 nM, respectively), but the concentration of α₂-adrenoceptors is two times lower than that of α₁-adrenoceptors ( 12.77 ± 3.17 and 30.25 ± 1.78 fmol/mg protein, respectively). The efficiency (E = B _max/2K _d) of the ligand binding to α₁-adrenoceptors is 2.3 times higher than that to α₂-adrenoceptors (7.46 ± 1.32 and 3.29 ± 0.68 fmol/mg protein/nM, respectively. The data suggest that α₁- and α₂ -adrenoceptors in rat cerebral cortex exist as dimers.     

Structures and stability of N<Subscript>13</Subscript><Superscript>+</Superscript> and N<Subscript>13</Subscript><Superscript>−</Superscript> clusters

The structures and stabilities of eleven N₁₃ ⁺ and N₁₃ ^– isomers have been investigated with second-order Møller–Plesset (MP2) and density functional theory (DFT) methods. Five N₁₃ ⁺ isomers and six N₁₃ ^– isomers are all reasonable local minima on their potential energy hypersurfaces. The most stable N₁₃ ⁺ cation is structure C-2 with C_2v symmetry, which contains a pentazole ring and two N₄ open chains. It is different from those of the N₇ ⁺ and N₉ ⁺ clusters, but similar to the N₁₁ ⁺ cluster. Meanwhile, the most stable N₁₃ ^– structure A-2 is composed of a pentazole ring and a six-membered ring connected by two nitrogen atoms. It is not only different from those of the N₇ ^– and N₉ ^– clusters, but also from the N₁₁ ^– cluster. The decomposition pathways of structures C-2 and A-2 were investigated at the B3LYP/(aug)-cc-pVDZ level. From the barrier heights of the structures C-2 and A-2 decomposition processes, it is suggested that C-2 is difficult to observe experimentally and A-2 may be observed as a short-lived species. Figure Optimized geometrical parameters of N₁₃ ⁺ isomer C-2      

IF<Subscript>1</Subscript> distribution in HepG2 cells in relation to ecto–F<Subscript>0</Subscript>F<Subscript>1</Subscript>ATPsynthase and calmodulin

F₀F₁ATPsynthase is now known to be expressed as a plasma membrane receptor for several extracellular ligands. On hepatocytes, ecto–F₀F₁ATPsynthase binds apoA–I and triggers HDL endocytosis concomitant with ATP hydrolysis. Considering that inhibitor protein IF₁ was shown to regulate the hydrolytic activity of ecto–F₀F₁ATPsynthase and to interact with calmodulin (CaM) in vitro, we investigated the subcellular distributions of IF₁, calmodulin (CaM), OSCP and β subunits of F₀F₁ATPsynthase in HepG2 cells. Using immunofluorescence and Western blotting, we found that around 50% of total cellular IF₁ is localized outside mitochondria, a relevant amount of which is associated to the plasma membrane where we also found Ca²⁺–CaM, OSCP and β. Confocal microscopy showed that IF₁ colocalized with Ca²⁺–CaM on plasma membrane but not in mitochondria, suggesting that Ca²⁺–CaM may modulate the cell surface availability of IF₁ and thus its ability to inhibit ATP hydrolysis by ecto–F₀F₁ATPsynthase. These observations support a hypothesis that the IF₁–Ca²⁺–CaM complex, forming on plasma membrane, functions in the cellular regulation of HDL endocytosis by hepatocytes.     

A computer-aided quantum chemical study of the N<Stack><Subscript>15</Subscript><Superscript>−</Superscript></Stack> cluster

Ab initio (RHF, MP2) and Density Functional Theory (DFT) methods have been used to examine six isomers of the N15m cluster with the 6-31+G* basis set. Different from the known odd-numbered anionic N7m, N9m, and N11m clusters, in which the open-chain structures are the most stable species, the most stable N15m isomer is structure 1 (C1), which may be considered as a complex between the fragments cyclic N5m (D5h) and staggered N10 (D2d). The decomposition pathways of structure 2 (CS), containing two aromatic N5 rings connected by a N5 chain, and the open-chain structure 3 (C2v) were studied at the B3LYP/6-31+G* level of theory. Relative energies were refined at the level of B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G*+ZPE (B3LYP/6-31+G*). The barriers for N2 and N5m (D5h) fission reactions for structure 2 are predicted to be 18.2 and 14.2 kcal x mol(-1), respectively. The corresponding N2+N3m fission barrier for structure 3 is predicted to be 11.2 kcal x mol(-1). Supplementary material is available for this article if you access the article at http://dx.doi.org/10.1007/s00894-003-0118-0. A link in the frame on the left on that page takes you directly to the supplementary material. Figure Structure 1 of the N15m cluster, showing bond distances in A and bond angles in degrees     

Effects of Prostaglandins F<Subscript>2α</Subscript>, E<Subscript>2</Subscript> and E<Subscript>1</Subscript> on Fertility in Mice

PROSTAGLANDIN (PG) F_2αhas antifertility effects in many species^1–3 but there are conflicting suggestions as to its mechanism of action. For example, it may cause the degeneration of the corpus luteum by decreasing blood flow in the uteroovarian vein⁴; alternatively, its action may be due to a hypersecretion of luteinizing hormone (LH) by the pituitary^3,5. I have investigated the effects of PGF_2α, E₂ and E₁ on pregnancy in mice and examined the mechanism of action of PGF_2α.