Evaluation of gadoxetate disodium as a contrast agent for mouse liver imaging: comparison with gadobenate dimeglumine

We investigated the characteristics of gadoxetate disodium (Gd-EOB-DTPA) as a contrast agent for magnetic resonance imaging of the mouse liver. Mice were imaged sequentially under isoflurane anesthesia using a T1-weighted, three-dimensional fast low-angle shot (3D FLASH) sequence after an intravenous injection of Gd-EOB-DTPA or gadobenate dimeglumine (Gd-BOPTA), and the time course of the contrast effect was examined. The time course of the contrast effect of Gd-EOB-DTPA was also assessed after intravenous injection under pentobarbital anesthesia and after subcutaneous injection while awake or under isoflurane or pentobarbital anesthesia. Moreover, different doses of Gd-EOB-DTPA or Gd-BOPTA were injected subcutaneously into conscious mice, and the clarity of the liver border was evaluated visually. Intravenous injection under isoflurane anesthesia caused rapid contrast enhancement in the liver with both Gd-EOB-DTPA and Gd-BOPTA, and the contrast effect was 41% stronger with Gd-EOB-DTPA. Subcutaneous injection of Gd-EOB-DTPA caused delayed but favorable contrast enhancement in the liver. Washout of Gd-EOB-DTPA was faster in mice injected while awake than in those injected under anesthesia. After intravenous injection, washout was faster under pentobarbital anesthesia than under isoflurane anesthesia. The peak liver contrast was 11% and 18% stronger under pentobarbital anesthesia than under isoflurane anesthesia, after intravenous and subcutaneous injections, respectively. Subcutaneous injection of Gd-EOB-DTPA or Gd-BOPTA caused dose-dependent contrast effects in the liver. At a given dose, the contrast effect tended to be stronger and liver demarcation tended to be clearer with Gd-EOB-DTPA than with Gd-BOPTA. In conclusion, intravenous or subcutaneous injection of Gd-EOB-DTPA produces a favorable contrast effects in the mouse liver, indicating its potential in investigating mouse models of liver diseases. The contrast effects vary between conscious mice and anesthetized mice and among anesthetic agents used.     

Stereoselective Synthesis of the Proposed C79–C104 Fragment of Symbiodinolide

Stereoselective and streamlined synthesis of the proposed C79–C104 fragment 2 of symbiodinolide ( 1 ), a polyol marine natural product with a molecular weight of 2860, was achieved. In the synthetic route, the proposed C79–C104 fragment 2 was synthesized by utilizing a Julia–Kocienski olefination and subsequent Sharpless asymmetric dihydroxylation as key transformations in a convergent manner. Detailed comparison of the ¹³C NMR chemical shifts between the natural product and the synthetic C79–C104 fragment 2 revealed that the stereostructure at the C91–C99 carbon chain moiety of symbiodinolide ( 1 ) should be reinvestigated.     

Stereodivergent Synthesis and Stereochemical Reassignment of the C79–C104 Fragment of Symbiodinolide

We have synthesized eight possible diastereoisomers 3 a – h of the C79–C97 fragment of symbiodinolide ( 1 ) in a stereodivergent manner by utilizing a dithiane addition to the aldehyde as a key step. Comparison of the ¹³C NMR chemical shifts of the natural product 1 and the synthetic products 3 a – h indicated that the relative stereostructure of this fragment in symbiodinolide ( 1 ) is that represented in 3 a or f . We have stereodivergently synthesized eight possible diastereoisomers of the C94–C104 fragment 4 a – h , and we have compared their ¹³C NMR chemical shifts with those of the natural product, which established the relative stereochemistry of this fragment to be that described in diastereoisomers 4 a or e . By combining the stereostructural outcomes of the C79–C97 and C94–C104 fragments, we have proposed four candidate compounds of the C79–C104 fragment 2 a – d . We also synthesized diastereoisomers 2 a and b ( 2 a in the preceding article; Chem. Eur. J. 2015 , DOI: 10.1002/chem.201503880) by a Julia–Kocienski olefination and diastereoisomers 2 c and d by a Wittig reaction. By comparing the ¹³C NMR chemical shifts of natural symbiodinolide ( 1 ) with those of the synthetic products 2 a – d , we have reassigned the stereostructure of the C79–C104 fragment of natural product 1 to be that depicted in diastereoisomer 2 b .     

pH Change of buffer solution in a microcapillary chip and its suppression

During the electrophoresis separation of B- and T-cells from lymphocytes employing a microcapillary chip, they were found to become inactive in the reservoir after a short time. This was caused by the buffer solution becoming alkaline due to electrolysis. This was considered to take place in chips with small reservoir volumes. The pH change was confirmed by the ISFET (ion-sensitive field effect transistor) embedded in the chip. To suppress the pH change, two methods were studied. One is the insertion of a salt bridge just in front of and behind the capillary, thus introducing an electric potential but stopping flow of the acid and alkaline solutions into the capillary. The other is neutralization of the alkaline solution in the reservoir by injecting the acid solution produced in another capillary with the same structure by employing an electroosmotic flow (EOF) pump. Both methods achieved no pH change during electrophoresis measurements in the microcapillary.     

480—Redox and adsorption behaviour of some redox coenzymes involved in an electron-transport chain studied by the electro-optical technique

The redox and adsorption behaviour of some redox coenzymes involved in an electron-transport chain, i.e. ubiquinone-10 (CoQ), flavocoenzymes [flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)] and nicotinamide adenine dinucleotide (NAD⁺), has been studied at a gold electrode by cyclic voltammetry and specular reflectivity measurement. All the coenzymes investigated were found to participate in electron transport in adsorbed states on the electrode surface. Adsorbed CoQ and flavocoenzymes are reduced and the resulting products remain adsorbed at the surface. Contrary to them, adsorbed NAD⁺ is reduced and then desorbed immediately. Possible models for the surface orientation of adsorbed molecules were proposed based on the experimental data.Some analogies can be noted between the interfacial behaviour of these coenzymes at the electrode and that in mitochondria.     

Effect of diet on aflatoxin B1-DNA binding and aflatoxin B1-induced glutathione S-transferase placental form positive hepatic foci in the rat

Effects of diets on hepatic aflatoxin B1 (AFB1)- DNA binding and AFB1-induced glutathione S- transferase placental (GST-P) form positive hepatic foci have been examined in young male Fischer rats. Animals were fed either AIN-76A or Purina Chow (PC) diet for 1 wk before AFB1- DNA binding studies in vivo and in vitro. Animals were injected i.p. with AFB1 (1 mug/kg body wt) and 3 days later were given either AIN-76A or PC diet with or without 0.1% phenobarbital (PB) in their drinking water. All animals were sacrificed 10 wks after AFB1 dosing for analysis of AFB1-induced GST-P positive hepatic foci by immunochemistry. Two h after i.p. injection of AFB1, hepatic AFB1-DNA binding in AIN-76A fed rats was twice as much as those in PC fed animals without affecting GSH levels. There was no significant effect of diet on either cytochrome P-450 content, GSH levels or microsomal cytochrome P-450 mediated AFB1-DNA binding to exogenous DNA. There was a 40% increase in cytosolic GSH S-transferase activity with 1-chloro-2,4-dinitrobenzene as a substrate in PC fed animals compared to those given AIN- 76A diet. The number and area of AFB1-induced GST-P positive hepatic foci were twice and fivefold as much in AIN-76A fed compared to those in PC fed rats. The number of AFB1-induced GST-P positive foci was increased 5-10 fold in the presence of PB in both groups. In summary, the present data indicate that feeding of PC diet compared to AIN-76A diet inhibits the initiation phase whereas AIN-76A stimulates the promotion phase of AFB1 hepatocarcinogenesis in rats by inhibiting AFB1-DNA binding and increasing AFB1-induced hepatic foci respectively.     

Convergent total syntheses of gambierol and 16-epi-gambierol and their biological activities

The convergent total syntheses of gambierol (1) and 16-epi-gambierol (2) have been achieved. The ABC and FGH ring segments 4 and 5 were prepared from known compounds 6 and 13, respectively, by linear manners. The fragments prepared were connected by our own synthetic strategy including the intramolecular allylation of alpha-acetoxy ether followed by ring-closing metathesis to furnish the octacyclic ether 3. The diiodoalkene 45, prepared from 3, was converted to the Z-iodoalkene 50 via a novel and stereoselective hydrogenolysis followed by deprotection. Construction of the triene side chain was performed by the modified Stille coupling of 50 with the Z-vinylic stannane 41 to afford 1. The similar transformations were carried out on the epimeric octacycle 34 to give 2, which showed no toxicity against mice at the concentration of 14 mg/kg.     

A validated HPLC‐fluorescence method with a semi‐micro column for routine determination of homocysteine,cysteine and cysteamine,and the relation between the thiol derivatives in normal human plasma

A semi‐micro column HPLC‐fluorescence method for routine determination of thiol derivatives such as homocysteine (Hcy), cysteine (Cys) and cysteamine (CA) is described. The thiol derivatives labeled with ammonium‐7‐fluorobenzo‐2‐oxa‐1,3‐diazole‐4‐sulfonate (SBD‐F) were isocratically separated within 12 min on a semi‐micro ODS column (Daisopak‐SP‐120‐5‐ODS‐BP) with a mixture of 25 mm acetate buffer (pH 2.00) and CH₃CN as a mobile phase. The purity and similarity of SBD‐thiols by a multi‐wavelength fluorescence detector were more than 92.3 and 96.7%. The detection limits of Hcy, Cys and CA at a signal‐to‐noise ratio of 3 were 0.16, 0.47 and 0.03 µm , respectively. Furthermore validation parameters such as accuracy, precision and robustness of the proposed method showed satisfactory results. Almost 850 plasma sample injections (range 572–1076, n = 3) for a column could be performed without differences in retention time and peak heights of labels. As an application of the proposed method, the determination of thiol derivatives in normal human plasma (n = 103) was demonstrated. The correlation coefficients between Hcy vs Cys and Hcy vs CA were 0.38 and −0.35, respectively. Copyright © 2009 John Wiley & Sons, Ltd.