Interactions of alpha- and beta-N-acetyl-D-glucosamines with hen and turkey lysozymes.

The binding constants of alpha- and beta-GlcNAc to hen and turkey lysozymes [EC 3.2.1.17] were determined at various pH's using the method proposed by Ikeda and Hamaguchi (1975) J. Biochem. 77, 1-16). The pH dependence of the binding of beta-GlcNAc to hen lysozyme was essentially the same as that for turkey lysozyme. The pH dependence curves of the binding constants of beta-GlcNAc to hen and turkey lysozymes were interpreted in terms of the participation of Glu 35 (pK 6.0), Asp 52 (pK 3.5), Asp 48 (pK 4.5), and Asp 66 (pK 1.5). The binding constants of alpha-GlcNAc to hen and turkey lysozymes were the same below pH 3.5 but were different above this pH. The main participant residues in the binding of alpha-GlcNAc were Glu 35, Asp 48, and Asp 66 for hen lysozyme and Glu 35 and Asp 66 for turkey lysozyme. The results obtained here were well explained by the following assumptions: (1) above about pH 4, alpha-GlcNAc binds to hen lysozyme in both alpha- and beta-modes, which correspond to the binding orientation of alpha-GlcNAc and that of beta-GlcNAc, respectively, as determined by X-ray crystallographic studies, but it binds predominantly in the beta-mode below about pH 4, (2) beta-GlcNAc binds to hen and turkey lysozymes predominantly in the beta-mode above about pH 4 and in both alpha- and beta-modes below pH 4, and (3) alpha-GlcNAc binds to turkey lysozyme predominantly in the beta-mode over the whole pH range studied.     

Inhibition of bull and rabbit sperm enzymes by alpha-chlorohydrin.

High concentrations of alpha-chlorohydrin were found to inhibit hyaluronidase, beta-glucuronidase, and aryl sulphatases in bull and rabbit spermatozoa, but not acrosin and neuraminidase. Preincubation of the enzyme and alpha-chlorohydrin was essential to achieve the maximum inhibition which was irreversible.     

Inhibition of in Vivo Conversion of Methionine to Ethylene by l-Canaline and 2,4-Dinitrophenol

l-Canaline, a potent inhibitor of pyridoxal phosphate-mediated reactions, markedly inhibited the conversion of methionine to ethylene and carbon dioxide by apple tissue. A 50% inhibition of methionine conversion into ethylene was obtained with 50 mum canaline and almost complete inhibition with 300 mum canaline. When 2,4-dinitrophenol, an oxidative phosphorylation uncoupler, was fed to apple tissue, it inhibited the conversion of radioactive methionine to ethylene by 50% at a concentration of 60 mum and by 90% at a concentration of 100 mum. Production of labeled carbon dioxide from acetate-1-(14)C was increased by 2,4-dinitrophenol, indicating that the inhibition of ethylene production was due to uncoupling of phosphorylation. Auxin-induced ethylene production by mungbean (Phaseolus mungo L.) hypocotyl sections was similarly inhibited by these inhibitors.These results support the proposal that pyridoxal phosphate is involved in the formation of ethylene from methionine, substantiate the requirement for ATP in ethylene production, and suggest that this ATP requirement occurs in the step (s) between methionine and ethylene. The biosynthetic mechanism probably involves activation of methionine by ATP followed by a pyridoxal phosphate-mediated gamma-elimination.     

Narcotic antagonist activity of several metabolites of naloxone and naltrexone tested in morphine dependent mice (38558).

A rabbit liver enzyme system was used to produce the 6beta-OH reduced metabolites of naloxone and naltrexone. GC analysis indicated the presence of some 6alpha-OH metabolite in these samples. The narcotic antagonist activity of these 6beta-OH metabolite samples were compared to naloxone, naltrexone and standard 6alpha-OH naltrexone (EN-2260A) using the jumping response of morphine pellet implanted mice. For the naloxone series, the potencies were: Naloxone greater than EN 2265A greater than 6 beta-OH maloxone. For the naltrexone series: Naltrexone greater than EN 2260A greater than beta-OH naltrexone. The low potency of the reduced metabolites the rapid onset of action of the parent compounds militate against the formation of these metabolites contributing substantially to the overall narcotic antagonist action of the parent compounds.     

益生菌调控肠道屏障功能预防家禽球虫病的研究进展

球虫病给养禽业带来巨大经济损失,人们对绿色健康食品的迫切需求使球虫病的防控面临新的挑战.伴随世界"禁抗"进程的不断推进,家禽养殖业亟需一种安全有效的新型抗球虫方法.益生菌可竞争性排斥病原菌定殖以防止球虫病继发感染,可刺激宿主抗菌肽、黏蛋白和紧密连接蛋白的分泌以抵御球虫入侵,还可激活免疫反应以增强机体抗球虫感染的能力.本...     

Development and Validation of a DNA Methylation-related Classifier of Circulating Tumour Cells to Predict Prognosis and to provide a therapeutic strategy in Lung Adenocarcinoma

Background: A significant factor influencing the prognosis of lung adenocarcinoma (LUAD) is tumor metastasis. Studies have shown that abnormal DNA methylation in circulating tumor cells (CTCs) is associated with tumour metastasis. Based on the genes expressed in CTCs that play an important role in DNA methylation, we hope to build a risk model to predict prognosis and provide a therapeutic strategy in LUAD.Methods: The CTC sequencing data for LUAD were obtained from {"type":"entrez-geo","attrs":{"text":"GSE74639","term_id":"74639"}}GSE74639, which contains 10 CTC samples and 6 primary tumour samples. To carefully assess the clinical value, functional status, involvement of the tumor microenvironment (TME) based on the risk model, and genetic variants based on based on data from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO), a reliable risk model was successfully built.Results: Three differentially methylated genes (DMGs) of CTCs for LUAD, including mitochondrial ribosomal protein L51 (MRPL51), STE20-like kinase (SLK), and protein regulator of cytokinesis 1(PRC1), were effectively used to construct a risk model. Both the training and validation cohorts'' stability and accuracy of the risk model were evaluated. Each patient in the TCGA-LUAD cohort received a risk score, and based on the median score, they were divided into high- and low-risk groups. The tumors in the high-risk group in this study were classified as "cold" and immunosuppressed, which may be linked to a poor prognosis. The tumors in the low-risk group, however, were deemed "hot" and had immune hyperfunction linked to a positive prognosis. Additionally, patients in the low-risk group showed greater sensitivity to immunotherapy than those in the high-risk group.Conclusions: Based on DMGs of CTCs from LUAD, we successfully developed a predictive risk model and discovered differences in biological function, TME, genetic variation, and clinical outcomes between those at high and low risk group.     

粤北南岭大宝山矿流域山水林田湖草修复阻力与优先级分析

遵循“防源、控流、治汇”理念,以粤北南岭大宝山矿区作为风险源,以所在流域为研究区,分析研究区主要阻力因素,采用最小累积阻力模型建立区域生态阻力面;利用Jenks自然断点法,分析生态修复优先级,提出分区治理重点和对策。研究结果表明：研究区综合阻力系数处于9-32之间,各评价指标的阻力面空间分布格局相似,其阻力值呈现出东南部大,西北部小的空间格局;长期的矿业开采污染了流域生态环境,且距离矿区越近的区域生态修复的优先性越高。将研究区分为4个优先级区,各区修复优先性依次为Ⅰ区 > Ⅱ区 > Ⅲ区 > Ⅳ区。Ⅰ区重点在于治水,提高pH、降低重金属有效态含量和增加地表植被覆盖度。Ⅱ区重点在于河流治理与治土,确保污染减排,增强拦泥库的废水调节。Ⅲ区、Ⅳ区核心在治土,逐步改善土壤条件。研究结果为修复项目在时空尺度上落地和科学治理提供科学依据。     

乳粉中嗜热菌污染研究进展

嗜热菌是乳粉中的常见污染菌,是影响乳粉品质的一个重要因素。本文综述乳粉中嗜热菌的种类、污染源对乳品工业的危害及其控制手段的研究进展,为国内相关领域研究提供参考。