[Behavioral and physiological responses to hypoxia stress in male and female Macrobrachium rosenbergii]. / 雌雄罗氏沼虾应对低氧胁迫的行为生理响应.

To explore the physiological and behavioral responses of male and female Macrobrachium rosenbergii under hypoxia stress, an experiment with three dissolved oxygen (DO) levels (6.46, 4.48 and 3.27 mg·L-1, 6.46 mg·L-1 as control) was conducted. The enzyme activities of energy metabolism in hepatopancreas and muscles of male and female M. rosenbergii were measured after six days of hypoxia stress. The results showed that the enzyme activities of aerobic metabolism in muscles and swimming abilities were significantly decreased as DO decreased from 6.46 mg·L-1 to 4.48 mg·L-1, with the decreases being less in males than females. There was no significant difference in enzyme activities of anaerobic metabolism. When DO was further decreased to 3.27 mg·L-1, the enzyme activities of aerobic metabolism and anaerobic metabolism in muscles significantly decreased. The activity of lactate dehydrogenase (LDH) in anaerobic metabolism of hepatopancreas and tail-flipping speeds significantly decreased in males and females, with less decrease in females than that in males for LDH activity of hepatopancreas. The swimming ability was positively correlated with the enzyme activities of aerobic metabolism in pleopods muscles. There was significant correlation between tail-flipping abilities and enzyme activities of anaerobic metabolism. M. rosenbergii could reduce its reliance on energy metabolism during hypoxia stress, but with negative consequences on locomotor abilities. The muscles were preferentially powered to meet energy requirements of locomotion in males, while females gave priority to energy supply for hepatopancreas under insufficient oxygen conditions.

Interaction between carbon cycling and phytoplankton community succession in hydropower reservoirs: Evidence from stable carbon isotope analysis.

Carbon (C) cycling and phytoplankton community succession are very important for hydropower reservoir ecosystems; however, whether the former controls the latter or the reverse is still debated. To understand this process, we investigated phytoplankton species compositions, stable C isotope compositions of dissolved inorganic C and particulate organic C (δ13C-DIC and δ13C-POC), and related environmental factors in seven hydropower reservoirs on the Wujiang River, Southwest China. A total of 36 algal genera from seven phyla were identified, and phytoplankton community exhibited obvious temporal and spatial difference. The δ13C-DIC (from -9.96 to -3.73‰) and δ13C-POC (from -33.44 to -21.17‰) co-varied with the algal species succession and increased markedly during the shift of dominant species from Bacillariophyta to Pyrrophyta or Cyanophyta. In addition, the strong C fixation in the euphotic layer resulted in great δ13C-DIC and CO2 stratification in the reservoir profile. Statistical analyses and C isotope evidence demonstrate that an increase in water temperature triggers phytoplankton community succession, and that CO2 availability is a key to drive the succession direction, and in turn, C cycling is enhanced when phytoplankton are dominated by Pyrrophyta or Cyanophyta in hydropower reservoirs. This study confirms that C cycling and phytoplankton community succession interact with each other and evolve synchronously, and will be helpful to systematically evaluate the environmental consequences of river damming.

Association between genetic polymorphism of heme oxygenase 1 promoter and neonatal hyperbilirubinemia: a meta-analysis.

Objective: The association between a (GT)n dinucleotide length polymorphism in the promoter region of heme oxygenase 1 (HMOX1) and the risk of neonatal hyperbilirubinemia remains controversial. This meta-analysis was, therefore, performed with aims to examine the correlation between the HMOX1 (GT)n repeat length polymorphism and neonatal hyperbilirubinemia susceptibility.Materials and methods: We searched the databases including PubMed, Embase, Cochrane Library, China national knowledge infrastructure (CNKI), and Wanfang Data, with all reviewed studies published before 28 June 2018. After the evaluation of quality, we used RevMan to perform the meta-analyses. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the effect of HMOX1 gene promoter polymorphisms on the risk of neonatal hyperbilirubinemia.Results: Seven studies, involving 584 patients with neonatal hyperbilirubinemia and 1655 controls, were included. A statistically significant association was found between the HMOX1 (GT)n repeat length polymorphism and risk of neonatal hyperbilirubinemia under the allele (allele S vs. allele L: OR = 1.81, 95% CI = 1.22-2.67, p = .003), recessive (genotype SS vs. genotypes LS + LL: OR = 1.38, 95% CI = 1.02-1.86, p = .04), dominant (genotypes SS + LS vs. LL: OR = 1.37, 95% CI = 1.01-1.76, p = .01), and homozygous genetic models (genotype SS vs. genotype LL: OR = 1.47, 95% CI = 1.02-2.11, p = .003), but not under the heterozygous genetic model. Interestingly, subgroup analysis revealed that the cutoffs of the S allele < 25 showed significant associations in any of the five genetic models (allele S vs. allele L: OR = 2.26, 95% CI = 1.68-3.05, p < .00001; genotype SS vs. genotypes LS + LL: OR = 2.56, 95% CI = 1.41-4.65, p = .002; genotypes SS + LS vs. genotype LL: OR = 1.82, 95% CI = 1.28-2.59, p = .0009; genotype SS vs. genotype LL: OR = 3.09, 95% CI = 1.50-6.36, p = .002; genotype LS vs. genotype LL: OR = 1.64, 95% CI = 1.11-2.42, p = .01); however, this association was not observed in the cutoffs of the S allele ≥25.Conclusion: The results of this study indicate that there is a significant association between the HMOX1 (GT)n repeat length polymorphism and susceptibility to neonatal hyperbilirubinemia. Newborns carrying shorter (GT)n repeats in the HMOX1 gene promoter may have a higher risk of neonatal hyperbilirubinemia.

Synthesis, molecular modeling, and biological evaluation of novel RAD51 inhibitors.

RAD51 recombinase plays a critical role for cancer cell proliferation and survival. Targeting RAD51 is therefore an attractive strategy for treating difficult-to-treat cancers, e.g. triple negative breast cancers which are often resistant to existing therapeutics. To this end, we have designed, synthesized and evaluated a panel of new RAD51 inhibitors, denoted IBR compounds. Among these compounds, we have identified a novel small molecule RAD51 inhibitor, IBR120, which exhibited a 4.8-fold improved growth inhibition activity in triple negative human breast cancer cell line MBA-MD-468. IBR120 also inhibited the proliferation of a broad spectrum of other cancer cell types. Approximately 10-fold difference between the IC50 values in normal and cancer cells were observed. Moreover, IBR120 was capable of disrupting RAD51 multimerization, impairing homologous recombination repair, and inducing apoptotic cell death. Therefore, these novel RAD51 inhibitors may serve as potential candidates for the development of pharmaceutical strategies against difficult-to-treat cancers.

A novel small molecule RAD51 inactivator overcomes imatinib-resistance in chronic myeloid leukaemia.

RAD51 recombinase activity plays a critical role for cancer cell proliferation and survival, and often contributes to drug-resistance. Abnormally elevated RAD51 function and hyperactive homologous recombination (HR) rates have been found in a panel of cancers, including breast cancer and chronic myeloid leukaemia (CML). Directly targeting RAD51 and attenuating the deregulated RAD51 activity has therefore been proposed as an alternative and supplementary strategy for cancer treatment. Here we show that a newly identified small molecule, IBR2, disrupts RAD51 multimerization, accelerates proteasome-mediated RAD51 protein degradation, reduces ionizing radiation-induced RAD51 foci formation, impairs HR, inhibits cancer cell growth and induces apoptosis. In a murine imatinib-resistant CML model bearing the T315I Bcr-abl mutation, IBR2, but not imatinib, significantly prolonged animal survival. Moreover, IBR2 effectively inhibits the proliferation of CD34(+) progenitor cells from CML patients resistant to known BCR-ABL inhibitors. Therefore, small molecule inhibitors of RAD51 may suggest a novel class of broad-spectrum therapeutics for difficult-to-treat cancers.

Synthesis of gem-difluoromethylenated analogues of boronolide.

The straightforward synthesis of four gem-difluoromethylenated analogues 4-7 of boronolide is described. The key steps of the synthesis include the concise preparation of the key intermediates 12a-b through the indium-mediated gem-difluoropropargylation of aldehyde 9 with the fluorine-containing building block 11 and the efficient construction of alpha,beta-unsaturated-delta-lactones 15a-b via BAIB/TEMPO-procedure.

Synthesis and biological evaluation of a series of novel inhibitor of Nek2/Hec1 analogues.

High expression in cancer 1 (Hec1) is an oncogene overly expressed in many human cancers. Small molecule inhibitor of Nek2/Hec1 (INH) targeting the Hec1 and its regulator, Nek2, in the mitotic pathway, was identified to inactivate Hec1/Nek2 function mediated by protein degradation that subsequently leads to chromosome mis-segregation and cell death. To further improve the efficacy of INH, a series of INH analogues were designed, synthesized, and evaluated. Among these 33 newly synthesized analogues, three of them, 6, 13, and 21, have 6-8 fold more potent cell killing activity than the previous lead compound INH1. Compounds 6 and 21 were chosen for analyzing the underlying action mechanism. They target directly the Hec1/Nek2 pathway and cause chromosome mis-alignment as well as cell death, a mechanism similar to that of INH1. This initial exploration of structural/functional relationship of INH may advance the progress for developing clinically applicable INH analogue.

Stereoselective synthesis of chiral IBR2 analogues.

Two stereoselective routes were developed to synthesize optically pure IBR2 analogues 1-16. The first features addition of N-Boc-3-bromoindole 26 to the sulfinamide 25, providing a 1:1 ratio of the separable diasteroisomers 27 and 28 in good yield. In a straightforward fashion, the sulfinamides 27 and 28 were conveniently converted into the key amines 39 and 47 over 8 steps, respectively, from which a series of 3,4-dihydroisoquinolinyl IBR2 analogues 1-14 containing fluorinated and trifluoromethylated benzyl groups were prepared. Another route highlights the highly enantioselective addition of indole to the sulfonyl amide 50 with bifunctional aminothioureas 57 and 58 as catalysts. After the reaction conditions were optimized, the desired sulfonyl amides (R)-55 and (S)-55 were obtained in 99% ee and 98% ee, respectively. Acylation of (R)-55 and (S)-55 separately and subsequent allylation gave compounds 60 and 63, respectively, which were further subjected to RCM to furnish compounds 61 and 64 and, after removal of the Boc groups, the desired IBR2 analogues 15 and 16.

Small molecule targeting the Hec1/Nek2 mitotic pathway suppresses tumor cell growth in culture and in animal.

Hec1 is a conserved mitotic regulator critical for spindle checkpoint control, kinetochore functionality, and cell survival. Overexpression of Hec1 has been detected in a variety of human cancers and is linked to poor prognosis of primary breast cancers. Through a chemical genetic screening, we have identified a small molecule, N-(4-[2,4-dimethyl-phenyl]-thiazol-2-yl)-benzamide (INH1), which specifically disrupts the Hec1/Nek2 interaction via direct Hec1 binding. Treating cells with INH1 triggered reduction of kinetochore-bound Hec1 as well as global Nek2 protein level, consequently leading to metaphase chromosome misalignment, spindle aberrancy, and eventual cell death. INH1 effectively inhibited the proliferation of multiple human breast cancer cell lines in culture (GI(50), 10-21 micromol/L). Furthermore, treatment with INH1 retarded tumor growth in a nude mouse model bearing xenografts derived from the human breast cancer line MDA-MB-468, with no apparent side effects. This study suggests that the Hec1/Nek2 pathway may serve as a novel mitotic target for cancer intervention by small compounds.

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates.

We present a mechanistic investigation of Pd-catalyzed allylic substitution of cyclic gem-difluorinated carbonates 1 and 4, previously employed in the synthesis of 3',3'-difluoro-2'-hydroxymethyl-4',5'-unsaturated carbocyclic nucleosides in 17 steps. The substitution features a reversal of regioselectivity caused by fluorine.

Synthesis of 3',3'-difluoro-2'- hydroxymethyl-4',5'-unsaturated carbocyclic nucleosides.

3',3'-Difluoro-2'-hydroxymethyl-4',5'-unsaturated carbocyclic nucleosides 1-3 have been stereoselectively synthesized from ester 10, which can be conveniently prepared from 2,3-isopropylidene-d-glyceraldehyde 7 in five steps. The whole synthesis highlighted the stereoselective Reformatskii-Claisen rearrangement, ring-closing metathesis (RCM), and palladium-catalyzed allylic alkylation, in which the regioselectivity was reversed from that of nonfluorinated substrates.

Synthesis of L-beta-3'-deoxy-3',3'-difluoro-4'-thionucleosides.

[Structure: see text] An efficient route to L-beta-3'-deoxy-3',3'-difluoro-4'-thionucleosides, thio-containing analogues of highly bioactive gemcitabine, is described. Our synthesis highlighted the installation of the thioacetyl group in high efficiency and construction of 3-deoxy-3,3-difluorothiofuranose skeleton in a novel method.

Indium-mediated diastereoselective allylation of D- and L-glyceraldimines with 4-bromo-1,1,1-trifluoro-2-butene: highly stereoselective synthesis of 4,4,4-trifluoroisoleucines and 4,4,4-trifluorovaline.

A practical and efficient route for the stereoselective synthesis of (2R,3S)- and (2S,3R)-4,4,4-trifluoroisoleucines and (2R,3S)-4,4,4-trifluorovaline was developed. Indium-mediated allylation of (R)-N-benzyl-2,3-O-isopropylideneglyceraldimine 7 with 4-bromo-1,1,1-trifluoro-2-butene 4 gave the desired homoallylic amine 8 in high diastereoselectivity (>95% de) with moderate yield. The Cbz-protected (2R,3S)-4,4,4-trifluoroisoleucine 14 and Boc-protected (2R,3S)-4,4,4-trifluorovaline 21 were then readily prepared from 8. In addition, following the same procedure, Cbz-protected (2S,3R)-4,4,4-trifluoroisoleucine 28, the enantiomer of 14, was prepared starting from (S)-N-benzyl-2,3-O-isopropylideneglyceraldimine 24.

Synthesis and biological evaluation of glycosidase inhibitors: gem-difluoromethylenated nojirimycin analogues.

In our ongoing program aimed at the design, synthesis, and biological evaluation of novel gem-difluoromethylenated glycosidase inhibitors, gem-4,4-difluoromethylenated iminosugars (5-9) were synthesized. The biological evaluation of these synthetic iminosugars showed that the gem-difluoromethylenyl group generally reduced the inhibition of glycosidases. However, this was not the case at pH 5.0, where the gem-difluoromethylenated iminosugar 6 was a stronger inhibitor than comparable iminosugars 1 and 36, suggesting that the influence of this group is mainly through its effect on the amine. It is proposed that the unprotonated iminosugar is the species preferably bound by beta-glucosidase, due to the lower pK(a) value of iminosugar 6 than of 1 or 36, leaving iminosugars 1 and 36 mostly protonated at pH 5.0, while iminosugar 6 is not. Iminosugar 6 also displayed good and selective inhibition of beta-glucosidase at pH 6.8.

Synthesis of L- and D-beta-3'-Deoxy-3',3'-difluoronucleosides.

Both L- and D-beta-3'-deoxy-3',3'-difluoronucleosides were synthesized starting from the key intermediate difluorohomoallyl alcohol 11. Deoxo-Fluor was accidentally found to be efficient in reversing the hydroxyl configuration of 34, and the desired product 41 was provided in good yield.

Synthesis and transformation of [difluoro(phenylseleno)methyl]- trimethylsilane.

[reaction: see text] A novel and efficient strategy was developed to synthesize [difluoro(phenylseleno)methyl]trimethylsilane (PhSeCF(2)TMS, 2), which was further utilized as a nucleophilic difluoromethylating reagent to incorporate the difluoro(phenylseleno)methyl (PhSeCF(2)) group into carbonyl compounds in good yields. The resulting PhSeCF(2)-containing alcohols 3 could be conveniently converted into corresponding difluoromethyl alcohols 4 by a radical deselenylation.

Synthesis of 3'-deoxy-3'-difluoromethyl azanucleosides from trans-4-hydroxy-l-proline.

[reaction: see text] Two strategies were tried to synthesize 3'-deoxy-3'-difluoromethyl azanucleosides. After the failure of the first route, the key intermediate 12 from trans-4-hydroxyproline 7 in 8 steps was stereoselectively prepared. The alcohol 12 was subjected to selective protection, oxidation, and difluoromethylenation to afford the fluorinated compound 18, whose hydrogenation was then systematically investigated. After a series of transformations of protecting groups, the resultant compounds 22 and 23 were oxidized to the desired lactams 24 and 25, which were successfully utilized to synthesize our target molecules, 3'-deoxy-3'-difluoromethyl azanucleosides 33, 34a, 34b, and 35.

Synthesis of cis-4-trifluoromethyl- and cis-4-difluoromethyl-l-pyroglutamic acids.

Efforts to synthesize 4-trifluoromethyl- and 4-difluoromethyl-l-pyroglutamic acids are described. After many arduous efforts, we successfully synthesized our target molecules cis-4-trifluoromethyl-l-pyroglutamic acid 25 and cis-4-difluoromethyl-l-pyroglutamic acid 26 from trans-4-hydroxy-l-proline through oxidation of fluorinated prolinates with RuO(4).

Practical synthesis of Boc-protected cis-4-trifluoromethyl and cis-4-difluoromethyl-L- prolines.

A short, efficient, and diastereomerically pure synthesis of N-Boc-cis-4-trifluoromethyl-L-proline (7) and N-Boc-cis-4-difluoromethyl-L-proline (9) from N-Boc-4-oxo-L-proline (4) is described. The reaction of 4 with Me(3)SiCF(3) and the conversion of the carbonyl group of 4 into the difluoromethylene group are the key steps for the synthesis of 7 and 9, respectively.