Denaturation of glycinin by urea and guanidine hydrochloride

Denaturation of glycinin by urea and guanidine hydrochloride (GdnHC1) has been studied at 30° by viscosity and circular dichroism (CD) measurements. The kinetics of denaturation by 8M urea at 20, 30, 40 and 50°, and by 6M GdnHC1 at 20° have been measured by monitoring the increase in absorbance at 287 nm as a function of time. Viscosity increased with denaturant concentration and reached maximum value of 28 mL/g at 6M GdnHC1 and 7M urea. The (negative) molar ellipticity values in the region 250–200 nm decreased with increase in denaturant concentration. Analysis of viscosity and CD data indicated that both sets of data fitted the same curve of f_d (fraction of protein denatured) versus denaturant concentration. The kinetic data followed first order reaction kinetics, These suggest that denaturation of glycinin by urea/GdnHC1 is a two-state process and follows the same pattern as that of globular proteins.     

AKA、抗CCP、RF联合检测对类风湿性关节炎的诊断价值

目的 探讨抗角蛋白抗体(AKA)、抗环胍氨酸肽抗体(抗CCP)和类风湿因子(RF)联合检测对类风湿性关节炎(RA)的诊断价值.方法 收集自2006年12月至2011年12月期间在我院检查的RA患者120例,其他自身免疫病患者120例和健康对照者120例的血清,分别采用间接免疫荧光法、酶联免疫吸附试验(ELISA)和颗粒增强速率散射比浊法检测AKA、抗CCP和RF,比较3种抗体单独和联合检测对诊断RA的敏感性和特异性.结果 类风湿性关节炎患者三种抗体的阳性率均高于其他自身免疫病患者和健康对照者(P<0.05).抗CCP的敏感性、阳性预测值、阴性预测值均比其他两种抗体高、AKA的特异性最好.三种抗体联合检测诊断RA的敏感度可达84.17%,比单独检测单一抗体的敏感性都高.结论 联合检测AKA、抗CCP及RF对于RA的诊断和早期诊断具有重要的应用价值.     

Isoform-specific proteolysis of apolipoprotein-E in the brain

Apolipoprotein-E (apoE) plays important roles in neurobiology and the apoE4 isoform increases risk for Alzheimer's disease (AD). ApoE peptides are biologically active and may be produced in the brain. It is unclear if apoE proteolysis is dependent on isoform or AD status and this was addressed here. Hippocampus, frontal cortex, occipital lobe and cerebellum samples were homogenized into fractions that were soluble in Tris-buffered saline (TBS), Triton X-100 or guanidine hydrochloride and analysed for apoE fragmentation by Western blotting. Approximately 20% of apoE3 was detected as fragments and this was predominantly as a 25 kDa peptide in TBS-soluble fractions. The concentration of TBS-soluble apoE fragments was two- to three-fold higher in apoE3 compared to apoE4 subjects. This difference was observed in all areas of the brain examined and was not related to AD status. Cathepsin-D treatment generated apoE fragments that were very similar to those detected in brain, however, no apoE isoform-specific differences in susceptibility to cathepsin-D proteolysis were detected. This indicates that proteolytic processing of apoE to form soluble fragments in the human brain is dependent on apoE isoform but not AD status.     

Antagonism of the ruthenium red-induced paralysis in mice by 4-aminopyridine, guanidine and lanthanum

4-Aminopyridine and guanidine were administered intraperitoneally to mice during the complete flaccid paralysis induced by treatment with ruthenium red (RuR). At 1-8 min after 4-aminopyridine or guanidine the animals had recovered completely from the paralysis, whereas the control mice injected only with RuR remained paralytic for at least 60 min. Intraperitoneal injections of LaCl3 had no apparent effects on animal motility and did not reverse the paralysis produced by RuR. However, when La3 + was administered 30 min prior to RuR the occurrence of flaccid paralysis was totally prevented. The results obtained are discussed in terms of the possible antagonist effects of the compounds used on acetylcholine release at neuromuscular junctions.     

Embryotoxic Effects of Acrolein,Methacrylates, Guanidines and Resorcinol on Three Day Chicken Embryos

Abstract: Acrolein, four methacrylates, two guanidine compounds and resorcinol were tested for embryotoxicity on three day chicken embryos. The most potent chemical was acrolein, with the ED50 0.05 μmol per egg for the total effect, including deaths and malformations. The substances next in potency were N,N'-di-o-tolyl-guanidine and N,N-diphenylguanidine, with ED50 values 0.17 and 0.20 μmol per egg, respectively. Resorcinol and the methacrylates had ED50 values ranging from 2.4 to 22.0 μmol per egg. Acrolein, diphenylguanidine, tetrahydrofururylmethacrylate and trimethylolpropanetrimethacrylate caused the largest amounts of malformed embryos.     

聚六亚甲基双胍复方消毒剂毒性试验观察

目的聚六亚甲基双胍复方消毒剂是以盐酸聚六亚甲基双胍为主要成分的复方消毒液。采用动物毒性试验对其经口毒性、皮肤刺激试验性、蓄积毒性、致微核作用、小鼠精子致畸作用、致敏性进行了研究。结果小鼠经口LD50>5000mg/kg·bw,对皮肤刺激反应积分均值为0,小鼠蓄积系数k>5。无毒,对手无刺激,有弱蓄积毒性,无致微核作用、对雄性小鼠精子无致畸作用,无致敏作用,可用皮肤消毒。     

Agmatine containing axon terminals in rat hippocampus form synapses on pyramidal cells

We examined the cellular and subcellular localization of agmatine in the hippocampal CA1 region by immunocytochemistry. By light microscopy, agmatine-like immunoreactivity (agmatine-LI) was found primarily in the perikarya and dendritic profiles of pyramidal cells and in punctate processes preponderantly in stratum radiatum. Electron microscopy revealed that agmatine-LI was cytoplasmic and concentrated in ‘clusters' associated with mitochondria and tubular vesicles. In stratum radiatum, agmatine-LI was primarily in axons and axon terminals associated with small, synaptic vesicles. The terminals almost exclusively formed asymmetric synapses on the spines of dendrites, many of which originated from pyramidal cells. Some agmatine-LI also was present in shafts and spines of pyramidal cell dendrites and in astrocytic processes. The results demonstrate that agmatine in the hippocampus is found primarily in terminals forming excitatory (asymmetric) synapses on pyramidal cells, some of which contain agmatine-LI. These findings further implicate agmatine as an endogenous neurotransmitter which may be co-stored with -glutamate and may act in part in the rat hippocampus as a blocker of the N-methyl- -aspartate receptor and nitric oxide synthase.     

Synthesis and structure-activity relationship study of the new set of trypsin-like proteinase inhibitors

Anew set of 25 trypsin-like proteinase inhibitors was prepared and the inhibiting activity on trypsin, thrombin, plasmin and urokinase was measured. The structure-activity relationship is discussed. High inhibiting activities were observed in 4-guanidinobenzoic acid esters only. The replacement of this moiety for N-formamidinyl-isonipecotic acid or an arginine moiety caused almost total loss of the activity. In the series of 4-guanidinobenzoic acid esters, any important influence of the ester-groups reactivity was observed. The trypsin-thrombin selectivity in the compounds with the guanidine-remote carboxylic function was also observed.     

Comparison of antioxidant activities of aminoguanidine,methylguanidine and guanidine by luminol-enhanced chemiluminescence

1. The objective of this study was to investigate the ability of aminoguanidine, methylguanidine and guanidine to inhibit free radicals or metabolites generated by either stimulated human leucocytes or cell-free systems using luminol-enhanced chemiluminescence (CL).
2. Aminoguanidine (0.1 μM–10 mM), methylguanidine (10 μM–10 mM) and guanidine (10 μM–10 mM) produced concentration-dependent inhibition (96±0.1%, n=7, 59±1.3%, n=6, and 62±3%, n=6, P<0.05 at 10 mM, respectively) in FMLP-stimulated leucocytes CL.
3. In cell-free experiments, hydrogen peroxide (H₂O₂), hypochlorous acid (HOCl), hydroxyl radical and peroxynitrite-induced CL responses were initiated by hydrogen peroxide (3.5 mM), NaOCl (50 μM), FeSO₄ (40 nM) and peroxynitrite (20 nM), respectively. Aminoguanidine, methylguanidine and guanidine produced concentration-dependent inhibition in H₂O₂-(69±0.7%, n=7, 26±1%, n=6, and 15±0.5%, n=6, at 1 mM, respectively) and HOCl-(84±0.3%, n=6, 50±1%, n=6, and 29±1%, n=7, at 1 mM, respectively) induced luminol CL. Peroxynitrite-induced CL was markedly attenuated in a concentration-dependent manner by aminoguanidine (99±0.1%, n=6, at 10 mM), methylguanidine (5±0.2%, n=6, at 10 mM) and guanidine (27±0.4%, n=7, at 10 mM). However, inhibition with aminoguanidine was found to be more marked than with methylguanidine and guanidine. Aminoguanidine (95±0.5%, n=6, at 1 mM) and methylguanidine (25±1%, n=6, at 1 mM), but not guanidine (2±1%, n=6, at 1 mM), significantly decreased ferrous iron-induced CL.
4. Collectively, these data suggest that aminoguanidine and a high concentration (⩾0.1 mM) of methylguanidine have direct scavenging activities against H₂O₂, HOCl, hydroxyl radical and peroxynitrite. Guanidine, at a high concentration (⩾0.1 mM), scavenges H₂O₂, HOCl and peroxynitrite, but not the hydroxyl radical. These direct scavenging properties may contribute to inhibitory effects of these compounds on human leucocyte CL.

     

AG对大鼠慢性高眼压视网膜Caspase-9表达的影响

目的:研究慢性高眼压过程中大鼠视网膜Caspase-9表达的变化及应用AG对其表达的影响,探讨AG可能存在的对慢性高眼压视网膜的保护作用。方法:应用免疫组化、RT-PCR和Western blot的方法观察应用AG及未应用AG的慢性高眼压大鼠视网膜在慢性高眼压后不同时间点的形态学变化及Caspase-9表达的变化。结果:与正常对照组相比,随着高眼压时间的延长视网膜逐渐出现可察觉的形态学变化,于高眼压的第21d视网膜变薄,节细胞数量减少;在此过程中,Caspase-9表达增多,与形态学变化相一致。而应用AG者其形态学变化和Caspase-9表达变化较小。结论:凋亡相关基因Caspase-9在慢性高眼压视网膜损伤过程中发挥了作用,AG通过下调其表达对视网膜起保护作用。