Comparison of two methods for the measurement of rat liver methylmalonyl-coenzyme A mutase activity: HPLC and radioisotopic assays

Methylmalonyl-coenzyme A mutase (MCM) is a 5'-deoxyadenosylcobalamin-linked mitochondrial enzyme that catalyzes the isomerization of L-methylmalonyl-coenzyme A to succinyl-coenzyme A. In vitro assays of total and holo-MCM activities are important tools for investigating the cobalamin pathway. Several methods have been described for measuring MCM activity. The most commonly-used method is a radioassay based on the permanganate oxidation of DL[CH(3)-(14)C]methylmalonyl-coenzyme A, but radiometric methods are insensitive, laborious, and time-consuming. Therefore, we have compared this method with a nonradiometric assay, potentially most sensitive, based on the separation of methylmalonyl-coenzyme A and succinyl-coenzyme A by high performance liquid chromatography (HPLC). We determined the optimal assay conditions and the reproducibility and sensitivity of each technique. The results obtained by the two techniques were very different: the specific activities obtained by the permanganate oxidation method (0.039 +/- 0.013 nmol/min/mg protein for the holo-MCM activity and 1.90 +/- 0.69 nmol/min/mg protein for the total-MCM activity) were threefold lower than those obtained with the HPLC method (0.124 +/- 0.011 nmol/min/mg protein for the holo-MCM activity and 6.15 +/- 0.76 nmol/min/mg protein for the total-MCM activity). The coefficients of variation for the radiometric method (18.4-40.6%) were three to five times greater than those for the HPLC assay (3.5-12.2%). This demonstrates the lack of sensibility and reproducibility of the permanganate radioassay. Thus, the radiometric method is not suitable for measuring low mutase activities such as the holo activities in tissues. The intrinsic inconvenience of the radiometric assay indicates that the HPLC method is a method of choice for measuring MCM activity.     

Inhibition in vitro of lipogenic enzymes from bovine (Bos taurus) mammary tissue by methylmalonyl-coenzyme A and coenzyme A

Bovine mammary fatty acid synthetase was inhibited by approximately 50% by 40 microM methylmalonyl-CoA; this inhibition was competitive with respect to malonyl-CoA (apparent Ki = 11 microM). Similarly, 6.25 microM coenzyme A inhibited the synthetase by 35% and this inhibition was again competitive (apparent Ki = 1.7 microM). Apparent Km for malonyl-CoA was 29 microM. The short-chain dicarboxylic acids malonic, methylmalonic and ethylmalonic at high concentrations (160-320 microM) and ATP (5 mM) enhanced the synthetase activity by about 50% respectively; the activating effects of methylmalonic acid and ATP on the synthetase were additive. Methylmalonyl-CoA at 50 microM concentration inhibited the partially purified acetyl-CoA carboxylase uncompetitively by 10% and the propionyl-CoA carboxylase activity of the enzyme preparation competitively (apparent Ki = 21 microM) by 40%. Malonyl-CoA also inhibited the acetyl-CoA carboxylase activity competitively (apparent Ki = 7 microM) by 35% and the propionyl-CoA carboxylating activity of the preparation competitively (apparent Ki = 4 microM) by 82%. The possibility that methylmalonyl-CoA may be a causal factor in the aetiology of the low milk-fat syndrome in high yielding dairy cows is discussed.     

A/California/7/2009与A/California/4/2009病毒感染力比较

目的甲型H1N1流感病毒A/California/7/2009与A/California/4/2009病毒序列比较同源性在99%以上,本实验旨在比较两株病毒感染BALB/c小鼠研究感染力强弱。方法分别将A/California/7/2009（CA7）与A/California/4/2009（CA4）两株病毒分别连续10倍稀释后,对4~6周龄雌性BALB/c小鼠经乙醚麻醉后进行滴鼻攻毒,每个稀释度接种10只实验小鼠,测定CA7 MLD50为101.24/0.05 mL,检测小鼠感染、致病的多项指标,观察期为14 d。结果相同TCID50的CA7和CA4病毒感染小鼠,CA4感染小鼠后14 d内死亡率为20%,而CA7感染小鼠后8 d内死亡率为100%。CA7 106TCID50感染的小鼠病理表现为重度弥漫性间质性肺炎,CA4 106TCID50感染的小鼠病理表现为中度-重度间质性肺炎。结论在相同条件下,CA7感染力明显强于CA4。     

FOXM1c is activated by cyclin E/Cdk2, cyclin A/Cdk2, and cyclin A/Cdk1, but repressed by GSK-3alpha

Two different inhibitory domains, N-terminus and central domain, keep FOXM1c almost inactive despite its strong transactivation domain. Here, we demonstrate that cyclin E/Cdk2, cyclin A/Cdk2, and cyclin A/Cdk1 activate FOXM1c. Cyclin E/Cdk2 does not target its transactivation domain or its DNA-binding domain. Instead, its activating effect strictly depends on the presence of either the central domain or the N-terminus of FOXM1c and thus is completely lost if both inhibitory domains are deleted. Cyclin E/Cdk2 activates FOXM1c by releasing its transactivation domain from the repression by these two inhibitory domains. However, it does not directly increase the transactivation potential of the TAD. The DNA-binding is not affected by cyclin E/Cdk2, neither directly nor indirectly. These two activating effects of cyclin E/Cdk2 via central domain and N-terminus are additive. Cyclin A/Cdk2 and cyclin A/Cdk1 show similar characteristics. GSK-3alpha, another proliferation-associated kinase, represses FOXM1c.     

Viscidic acid A and B,two ent-labdane derivatives from Chrysothamnus viscidiflorus

The chemical investigation of Chrysothamnus viscidiflorus afforded, in addition to known bisabolene derivatives, elemicin and p-hydroxyacetophenone, two new diterpene acids. Their structures were determined, by spectroscopic methods and some chemical transformations, as ent-labd-8(17),13E-dien-15-ol-18-oic acid (viscidic acid A) and ent-labd-8(17),13E-dien-15-acetoxy-18-oic acid (visidic acid B).     

Regulation and induction of CYP3A11, CYP3A13 and CYP3A25 in C57BL/6J mouse liver

This study reports that dexamethasone (DEX) significantly induces CYP3A11, CYP3A13 and CYP3A25 mRNA expression in male and female 4 days, 3 weeks and 18 weeks old C57BL/6J mice. Furthermore, CYP3A activity, as measured by erythromycin-N-demethylation, is also significantly increased. PXR, RXRalpha and CAR are known to be involved in the induction of CYP3As. Here we report nuclear receptors PXR and RXRalpha but not CAR demonstrate gender- and age-dependent expression. Also, treatment of C57BL/6J mice with DEX induces PXR but not RXRalpha or CAR. In summary, we demonstrate DEX is not only able to up-regulate CYP3A expression and activity, but also the nuclear receptor PXR through which it may exert this effect. Furthermore, the gender- and age-dependent pattern of basal PXR and RXRalpha expression is similar to the 3 CYP3As analysed.     

A1/A2 polymorphism of GpIIIa gene and a risk of aneurysmal subarachnoid haemorrhage

Platelet glycoproteins are involved in pathophysiology of cerebrovascular diseases. The aim of this study was to investigate the association between the GpIIIa gene A1/A2 polymorphism and a risk of aneurysmal subarachnoid haemorrhage (SAH) in a Polish population. In a case-control study we genotyped 288 Caucasian patients with aneurysmal SAH and 457 age-, gender- and race-matched controls. The GpIIIa A1/A2 polymorphism was genotyped with RFLP technique. No difference was found in the distribution of the polymorphism between the cases and controls (cases: A1A1—201 (69.8%), A1A2—83 (28.8%) and A2A2—4 (1.4%) vs. controls: A1A1—323 (70.7%); A1A2—128 (28.0%); A2A2—6 (1.3%), P > 0.05. In a multivariate analysis female gender (OR = 1.950; 95%CI: 1.308-2.907), hypertension (OR = 4.774; 95%CI: 3.048-7.478) and smoking (OR = 2.034; 95%CI: 1.366-3.030), but not GpIIIa A1/A2 polymorphism, were independent risk factors for aneurysmal SAH. The GpIIIa A1/A2 polymorphism is not a risk factor of aneurysmal SAH in a Polish population.     

六种鲟鱼消化酶活性的比较研究

测定了两个生长阶段 6种鲟鱼幼鱼胃、肠道和肝脏中蛋白酶、脂肪酶、淀粉酶活性。幼鲟消化酶活性在两个生长阶段变化不明显。 6种鲟鱼不同消化器官蛋白酶活性以肠道为最高 ,肝脏为最低 ,肝脏中的蛋白酶活性明显低于胃、肠道 (P <0 0 1)。不同消化器官脂肪酶活性 ,以肠道为最高 ,且肠道脂肪酶活性显著高于胃、肝脏 (P <0 0 1) ,胃中的脂肪酶活性与肝脏中的脂肪酶活性差异不明显 (P >0 0 5 )。不同消化器官淀粉酶活性 ,以肠道为最高 ,且明显高于胃、肝脏 (P <0 0 1)。幼鲟在第一阶段 ,肝脏中没有淀粉酶活性 ,其活性出现在第二阶段 ,且在此生长阶段 ,肝脏中的淀粉酶活性达到胃中的水平 (P >0 0 5 )。对 6种鲟鱼而言 ,除个别存在较大差异外 ,3种消化酶活性大体上都没有明显差异     

The detection of the sialoglycoprotease gene and assay for sialoglycoprotease activity among isolates of Pasteurella haemolytica A1 strains, serotypes A13, A14, T15 and A16

Abstract Polymerase chain reaction (PCR) using specific primers to the sialoglycoprotease gene ( gcp ) of Pasteurella haemolytica biotype A, serotype 1 amplified a 1-kb fragment from each of P. haemolytica serotypes A7, A13, A14 and A16, but not T15; which was confirmed by Southern blot hybridization analysis. Using a sialoglycoprotease (Gcp) activity assay, Gcp activity was found in serotypes A13, A14 and A16. Inclusion of these three serotypes confirms that all recognized A biotypes are positive for both gcp gene and activity, with the exception of serotype A11 (which has a different genetic organization and exhibits no Gcp activity). Furthermore, all recognized T biotypes are negative for both the gene and Gcp activity.     

Tanacetols A and B,non-volatile sesquiterpene alcohols,from Tanacetum vulgare

Chemical investigation of a rare chemotype of Tanacetum vulgare attorded a series of non-volatile sesquiterpene alcohols which have been called tanacetols. The structures of tanacetols A and B, the two most abundant, have been established on the basis of spectroscopic data, chemical reactions and X-ray diffraction analysis of tanacetol A and tanacetol B acetate.     

Malonate, Malonyl-Coenzyme A, and Acetyl-Coenzyme A in Developing Rat Brain

Abstract: Free malonate, malonyl-coenzyme A (malonyl-CoA), and acetyl-CoA were assayed in rat brain at developmental ages from the 20th day of gestation to 60 days of postnatal life. The determination of malonate was based on its conversion to malonyl-CoA and decarboxylation to acetyl-CoA by enzyme extracts from Pseudo-monas fluorescens. The resulting acetyl-CoA reacted with [4-¹⁴C]oxaloacetate to form [5-¹⁴C]citrate, which was isolated by TLC. Malonyl-CoA in perchloric acid extracts from brain was converted to acetyl-CoA by rat liver mitochondrial malonyl-CoA decarboxylase (EC 4.1.1.9). Acetyl-CoA derived from this step was assayed by a modified CoA-cycling procedure. Brain acetyl-CoA was also assayed by CoA cycling. Prenatal brain contained no free malonate but malonyl-CoA was present. The acetyl-CoA level was relatively high just prior to birth and declined slightly with growth. Malonate concentrations after birth rose rapidly to reach 192 nmol/g wet weight at 60 days. Adult levels for malonyl-CoA and acetyl-CoA were 1.83 and 1.90 nmol/g wet weight, respectively. The origin and natural role of free malonate in brain are not known but deacylation of malonyl-CoA by reversal of the malonyl-CoA synthetase reaction is postulated. Rat liver and kidney also contain substantial concentrations of free malonate.     

Formation, Metabolism, and Action of Hepoxilin A3in the Rat Pineal Gland

Abstract: The present study was undertaken to investigate the possible formation of hepoxilin A₃ in the rat pineal gland and to study the potential physiological role for this compound in this tissue. Incubation of homogenates of rat pineal glands with arachidonic acid (66 μM) led to the appearance of hepoxilin A₃ (HxA₃) analyzed as its stable trihydroxy derivative, trioxilin A₃ by gas chromatography in both the electron impact and negative ion chemical ionization modes. Endogenous formation of HxA₃ is estimated to be 1.43 ± 0.66 ng//μg of protein. This amount is not modified when the tissue is boiled (2.07 ± 0.66 ng/μg of protein). However, the formation of this compound was stimulated to 21.26 ±5.82 ng/μg of protein when exogenous arachidonic acid was added to the homogenate. Addition of the dual cyclooxygenase/lipoxygenase inhibitor BW 755C (10 /μg) resulted in a partial blockade of hepoxilin formation. Using [1-¹⁴C] H×A₃, we demonstrated that the pineal gland contained hepoxilin epoxide hydrolase, which hydrolyzed HxA₃ into trioxilin A₃. This hydrolysis was inhibited by 1 μmol/L of 3, 3, 3-trichloropropene-1, 2-oxide. In a separate study, HxA₃ in the presence of 3, 3, 3-trichloropropene-1, 2-oxide to block the hydrolysis of HxA₃ decreased the production of cyclic AMP in cultured organ rat pineals after stimulation with 5′-N-ethylcarboxamidoadenosine, an A₁/A₂ adenosine receptor agonist. This effect is stereospecific because the (8S)-enantiomer is more active in decreasing cyclic AMP production (?88.7%) than the (8R)-enantiomer. This is the first demonstration of the presence, metabolism, and action of HxA₃ in the rat pineal gland.     

Violacin A,a new chromanone produced by Streptomyces violaceoruber and its anti-inflammatory activity

A new chromanone derivative, named violacin A (1), was isolated from the fermentation broth of Streptomyces violaceoruber as a potential anti-inflammatory compound. The structure of violacin A was established using comprehensive NMR spectroscopic data analysis together with UV, IR, and MS data. The anti-inflammatory effects and action mechanisms of violacin A were investigated in vitro. The results demonstrated that violacin A attenuated the production of NO, IL-1β, IL-6, and TNF-α as well as inhibited the expression of iNOS in LPS-induced RAW 264.7 cells. Additionally, Western blot and qRT-PCR results revealed that 1 down-regulated pro-inflammatory cytokines expression correlated with the suppression of NF-κB signaling pathway.     

外周血单核细胞CHOP、NLRP3、S100A8/A9 mRNA表达水平与脓毒症患者炎症反应和预后的关系分析

摘要 目的：探讨外周血单核细胞（PBMC）中CCAAT/增强子结合蛋白同源蛋白（CHOP）、核苷酸结合寡聚化结构域样受体蛋白3（NLRP3）、S100A8/A9 信使核糖核酸（mRNA）表达水平与脓毒症患者炎症反应和预后的关系。方法：选取2020年1月～2022年1月新疆维吾尔自治区人民医院收治的170例脓毒症患者为脓毒症组,另选取同期68名健康体检者为对照组。采用酶联免疫吸附法检测血清白介素（IL）-6、IL-10、IL-17、IL-23、转化生长因子-β（TGF-β）水平,实时荧光定量PCR（qRT-PCR）法检测PBMC中CHOP、NLRP3、S100A8/A9 mRNA表达水平,比较脓毒症组与对照组上述指标差异。采用Pearson/Spearman相关系数分析脓毒症患者PBMC中CHOP、NLRP3、S100A8/A9 mRNA表达水平与炎症因子水平的相关性。脓毒症患者根据28d预后差异分为死亡组和存活组,收集临床资料,采用多因素Logistic回归分析脓毒症患者预后的影响因素。结果：脓毒症组PBMC中CHOP、NLRP3、S100A8/A9 mRNA相对表达量和血清IL-6、IL-10、IL-17、IL-23、TGF-β水平均明显高于对照组（P＜0.05）。Pearson/Spearman相关性分析显示,脓毒症患者PBMC中CHOP、NLRP3、S100A8/A9 mRNA表达水平与血清IL-6、IL-10、IL-17、IL-23、TGF-β水平均呈正相关（P＜0.05）。不同预后脓毒症患者比较,死亡组年龄大于存活组,脓毒性休克、多器官功能障碍综合征（MODS）、ICU住院时间≥10 d、机械通气时间≥3 d患者比例、脓毒症相关器官衰竭评估（SOFA）评分、血乳酸、血清IL-6、IL-10、IL-17、IL-23、TGF-β水平以及PBMC中CHOP、NLRP3、S100A8/A9 mRNA相对表达量均高于存活组,而氧合指数低于存活组（P＜0.05）。多因素Logistic回归分析显示,校正其他因素后,PBMC中CHOP mRNA、NLRP3 mRNA、S100A8/A9 mRNA表达水平升高是脓毒症患者预后不良的危险因素（P＜0.05）。结论：脓毒症患者PBMC中CHOP、NLRP3、S100A8/A9 mRNA呈高表达,且表达水平与炎症反应及患者预后密切相关。     

Dianthramides A and B,two N-benzoylanthranilic acid derivatives from elicited tissues of Dianthus caryophyllus

Two new phenolic derivatives, dianthramide A and B, were isolated from Dianthus caryophyllus tissues elicited with mycelial extracts of Phytophthora parasitica. The purified substances were identified on the basis of their spectral data and were characterized as N-salicyl-4-methoxyanthranilic acid (dianthramide A) and N-salicyl-4-hydroxyanthranilic acid methyl ester (dianthramide B). Dianthramides A and B co-occur in carnation tissues with the known phytoalexin dianthalexin.     

甲硫氨酸腺苷转移酶1A/2A平衡与肝细胞癌

肝细胞癌是一种死亡率极高的癌症,大多数病人发现时已属晚期.甲硫氨酸腺苷转移酶(MAT)是细胞生命活动的关键酶,可以通过催化甲酼氨酸和三磷酸腺苷(ATP)结合,促进生物甲基供体S-腺苷甲酼氨酸(SAMe)的生物合成.正常肝细胞中MAT1A与MAT2A存在动态平衡,共同维持细胞内SAMe稳态;肝细胞癌中MAT1A转变成MAT2A,会使SAMe生物合成减少,为癌细胞生长提供有利条件,故MAT1A表达降低而MAT2A增高.因此,促进MAT2A向MAT1A转化,进而提高MAT1A/MAT2A的比值可能成为治疗肝细胞癌的关键靶点之一.本文就MAT1A/MAT2A平衡在肝细胞癌中的重要作用作一综述,旨在为寻找肝细胞癌防治靶点提供新的思路.