Comparative Genotypes,Staphylococcal Cassette Chromosome mec (SCCmec) Genes and Antimicrobial Resistance amongst Staphylococcus epidermidis and Staphylococcus haemolyticus Isolates from Infections in Humans and Companion Animals

This study compares the characteristics of Staphylococcus epidermidis (SE) and Staphylococcus haemolyticus (SH) isolates from epidemiologically unrelated infections in humans (Hu) (28 SE-Hu; 8 SH-Hu) and companion animals (CpA) (12 SE-CpA; 13 SH-CpA). All isolates underwent antimicrobial susceptibility testing, multilocus sequence typing and DNA microarray profiling to detect antimicrobial resistance and SCCmec-associated genes. All methicillin-resistant (MR) isolates (33/40 SE, 20/21 SH) underwent dru and mecA allele typing. Isolates were predominantly assigned to sequence types (STs) within a single clonal complex (CC2, SE, 84.8%; CC1, SH, 95.2%). SCCmec IV predominated among MRSE with ST2-MRSE-IVc common to both Hu (40.9%) and CpA (54.5%). Identical mecA alleles and nontypeable dru types (dts) were identified in one ST2-MRSE-IVc Hu and CpA isolate, however, all mecA alleles and 2/4 dts detected among 18 ST2-MRSE-IVc isolates were closely related, sharing >96.5% DNA sequence homology. Although only one ST-SCCmec type combination (ST1 with a non-typeable [NT] SCCmec NT9 [class C mec and ccrB4]) was common to four MRSH-Hu and one MRSH-CpA, all MRSH isolates were closely related based on similar STs, SCCmec genes (V/V_T or components thereof), mecA alleles and dts. Overall, 39.6% of MR isolates harbored NT SCCmec elements, and ACME was more common amongst MRSE and CpA isolates. Multidrug resistance (MDR) was detected among 96.7% of isolates but they differed in the prevalence of specific macrolide, aminoglycoside and trimethoprim resistance genes amongst SE and SH isolates. Ciprofloxacin, rifampicin, chloramphenicol [fexA, cat-pC221], tetracycline [tet(K)], aminoglycosides [aadD, aphA3] and fusidic acid [fusB] resistance was significantly more common amongst CpA isolates. SE and SH isolates causing infections in Hu and CpA hosts belong predominantly to STs within a single lineage, harboring similar but variable SCCmec genes, mecA alleles and dts. Host and staphylococcal species-specific characteristics were identified in relation to antimicrobial resistance genes and phenotypes, SCCmec and ACME.     

Classic Anthropology: Critical Essays: 1944-1996

Classic Anthropology: Critical Essays: 1944-1996. John W. Bennett. Piscataway, NJ: Transaction Publishers, 1998. 426 pp.     

Mitochondrion-dependent N-terminal processing of outer membrane Mcl-1 protein removes an essential Mule/Lasu1 protein-binding site

Mcl-1, a pro-survival member of the Bcl-2 family located at the mitochondrial outer membrane, is subject to constitutive ubiquitylation by the Bcl-2 homology 3-only E3 ligase, Mule/Lasu1, resulting in rapid steady-state degradation via the proteasome. Insertion of newly synthesized Mcl-1 into the mitochondrial outer membrane is dependent on its C-terminal transmembrane segment, but once inserted, the N terminus of a portion of the Mcl-1 molecules can be subject to proteolytic processing. Remarkably, this processing requires an intact electrochemical potential across the inner membrane. Three lines of evidence directed at the endogenous protein, however, indicate that the resulting Mcl-1ΔN isoform resides in the outer membrane: (i) full-length Mcl-1 and Mcl-1ΔN resist extraction by alkali but are accessible to exogenous protease; (ii) almost the entire populations of Mcl-1 and Mcl-1ΔN are accessible to the membrane-impermeant Cys-reactive agent 4-acetamido-4'-[(iodoacetyl)amino]stilbene-2,2'-disulfonic acid; and (iii) Mcl-1 and Mcl-1ΔN exhibit equivalent chemical cross-linking to Bak in intact mitochondria, an Mcl-1 binding partner located in the outer membrane. In addition to the Mule Bcl-2 homology 3 domain, we show that interaction between Mcl-1 and Mule also requires the extreme N terminus of Mcl-1, which is lacking in Mcl-1ΔN. Thus, Mcl-1ΔN does not interact with Mule, exhibits reduced steady-state ubiquitylation, evades the hyper-rapid steady-state degradation that is observed for full-length Mcl-1 in response to treatments that limit global protein synthesis, and confers resistance to UV stress-induced cell death.     

Effects of estrone and 17 β-estradiol on vegetative growth of Medicago sativa

Alfalfa ( Medicago sativa L.) plants were grown in the absence or presence of the steroidal estrogens, estrone and 17β-estradiol, under varying conditions. Plants were analysed for the following parameters: plant weight, estrogen content, phytoestrogen content, degree of nodulation and nitrogen fixation activity. It was found that under controlled greenhouse conditions: (1) Treatment with estrogens in the range of 0.005 to 0.5 μg 1⁻¹ increases both shoot and root dry weitht. In contrast, estrogen in concentrations of 50 to 500 μg 1⁻¹ decreases plant growth. (2) The effect of estrogen of growth is most marked in the absence of nitrogen. (3) Estrone is more effective in increasing growth than 17 β-estradiol. (4) In the plants where estrogen induced growth there was no significant increase in nitrogen fixation activity and nodule number. (5) Endogenous estrogen content of the plant did not increase at concentrations (0.005-0.5 μg 1⁻¹) which increased vegetative growth. (6) Endogenous estrogen content of the plant did increase at concentrations of estrogen (50-500 μg 1⁻¹ which inhibited vegetative growth and nodule weight. It can be concluded that estrogen in concentrations found in sewage water (0.3 μg estrogen 1⁻¹) can affect the vegetative growth of alfalfa plants.     

2个表达单元间相互位置和转录方向对表达的影响

目的:研究质粒表达载体中2个表达单元间相互位置和转录方向关系对表达的影响,找出利于2个表达单元表达的优化的相互关系。方法:以全抗体为研究对象,构建了轻重链方向不同的2种相互关系的单质粒表达载体pIRESdhfrA和pIRESdhfrB,转染CHO-dhfr-细胞后,对瞬时表达水平进行了比较。以pIRESdhfrA和pIRESdhfrB为基础,构建了瞬时表达载体pIRESdhfrA-sv40ori和pIRESdhfrB-sv40ori,在COS-7细胞中进行了瞬时表达水平的比较。构建了基于CHO定点细胞系的稳定表达细胞株,对pIRESdhfrA和pIRESdhfrB进行稳定表达水平的比较。结果:在CHO-dhfr-的瞬时表达水平比较中,pIRESdhfrB转染的细胞表达水平是pIRESdhfrA转染细胞的2.18倍。与pIRESdhfrA-sv40ori在COS-7细胞的瞬时表达水平相比,pIRESdhfrB-sv40ori是其表达水平的2.3倍。pIRESdhfrB-FRT构建的CHO定点细胞平均表达水平是pIRESdhfrA-FRT构建的CHO定点细胞的11.6倍。结论:在构建的真核细胞质粒表达载体pIRESdhfr中,2个表达盒的启动子头-头转录方向关系比头-尾方向关系更利于重组蛋白的表达。     

Increased sitosterol absorption, decreased removal, and expanded body pools compensate for reduced cholesterol synthesis in sitosterolemia with xanthomatosis

We measured the turnover and absorption of sitosterol and cholesterol, along with plasma sterol and lipoprotein concentrations, in one control and two subjects with sitosterolemia with xanthomatosis. All individuals consumed the same diet which contained approximately 500 mg/day of cholesterol and 250 mg/day of sitosterol. Sterol absorption was measured by the plasma dual-isotope ratio method and turnover by plasma isotope-kinetic analysis. In two sitosterolemic subjects, 28% and 63% of the sitosterol and 69% and 49% of the cholesterol were absorbed, respectively, compared to 4% of the sitosterol and 44% of the cholesterol in the control. As expected, plasma sitosterol specific activities decayed much more rapidly than cholesterol in the control subject. In contrast, plasma sitosterol and cholesterol specific activity-time curves were similar and decayed more slowly in the sitosterolemic subjects. In the control subject, the total sitotterol pool was 290 mg and was linearly related to low absorption (18 mg/day); whereas the total sitosterol pool was 17 times (4800 mg) and 13 times (3500 mg) larger, respectively, in the sitosterolemic subjects and was expanded out of proportion to increased absorption because of decreased removal. Daily cholesterol turnover and synthesis were markedly reduced in the sitosterolemic subjects. In four sitosterolemic subjects, plasma concentrations of total sterols, low density lipoproteins, and apolipoprotein B were increased, while those of high density lipoproteins and apolipoprotein A-I were low to normal. The low density lipoproteins were very similar to those of normal control subjects in density distribution, peak flotation rate, sterol-to-protein (apolipoprotein B) ratio, particle size, and morphology. These results demonstrate in patients with sitosterolemia with xanthomatosis that: 1) the absorption of sitosterol and cholesterol is enhanced; 2) tissue recognition between cholesterol and sitosterol is lost; 3) total exchangeable sitosterol pools are expanded out of proportion to absorption because of decreased excretion; 4) plasma sterol and lipoprotein concentrations favor tissue deposition; and 5) cholesterol synthesis is diminished. We postulate that the changes in sitosterol metabolism (increased absorption, loss of tissue sterol structural recognition, expanded pools, and hepatic retention) are a response to reduced cholesterol synthesis in these subject.     

贵州南部铝土矿的孢粉组合特征及沉积时代讨论*

铝土矿是一种重要的工业矿产资源。目前中国大部分的铝土矿依赖进口。因此, 研究铝土矿的沉积模式对我国的资源安全和矿产开发具有重要意义。铝土矿的成矿受多种因素影响, 包括大地构造背景、古气候、侵蚀速率、母岩、时间、古植被和古地形地貌等。要研究这些成矿因素对铝土矿的影响, 并为下一步的找矿勘察工作提供理论支撑, 首先需要准确评估铝土矿的沉积时代。然而, 由于铝土矿的沉积过程涉及复杂的土壤化作用和再沉积过程, 其中保存的植物根系化石或遗迹化石数量很少, 因此很难确定铝土矿的最终沉积时间。目前, 综合分析铝土矿中保存的孢粉化石组合是确定铝土矿沉积时代更有效的方法。在中国, 已经确定的铝土矿沉积时代主要集中在晚古生代。华南产出的晚古生代铝土矿主要以贵州铝土矿为代表, 然而长期以来对贵州铝土矿的形成时代存在较多争议。为了解决这些争议, 本研究在贵州龙里县龙山镇和花溪区高坡苗族乡的两个铝土矿地层剖面上进行了孢粉地层研究。研究结果显示, 贵州龙里县龙山镇SPM095和花溪区高坡苗族乡SPM097剖面的革老河组、汤耙沟组、丰源层铝土岩和祥摆组底部产出的孢粉组合与西欧密西西比亚纪标准Lycospora pussila (Pu)孢粉组合带基本相当, 表明丰源铝土矿的沉积时代不晚于密西西比亚纪维宪早中期, 这是目前已知贵州地区最早的具有明确化石证据的喀斯特型铝土矿。通过与贵州中部清镇至贵州北部遵义等地铝土矿中发现的孢粉组合进行对比, 发现丰源铝土矿中的孢粉组合比上述地区铝土矿中的孢粉组合大致低一个孢粉组合带 (Perotriletes tessellatus—Schulzosopra camplylotera组合带)或一个牙形刺带(Gnathodus bilineatus带), 时代大概相差420万年。这一发现进一步表明晚古生代大冰期(LPIA)引起的频繁海平面变化导致贵州“南海北陆”的古地理格局由南向北逐次被海水淹没, 并接受沉积, 这是导致贵州不同地区铝土矿呈现由南向北时代梯度递减的主要原因。