Damage to protein synthesis concurrent with lipid peroxidation in rat liver slices: effect of halogenated compounds, peroxides, and vitamin E1

Protein synthesis and lipid peroxidation were evaluated in rat liver slices incubated in the presence of oxidants and protein synthesis inhibitors. Protein synthesis by rat liver slices was evaluated by [3H]leucine incorporation into the trichloroacetic acid (TCA)-insoluble material, and lipid peroxidation was evaluated by thiobarbituric acid-reactive substances (TBARS) released into the incubation medium. Protein synthesis inhibition by bromotrichloromethane (BrCCl3) or t-butyl hydroperoxide (t-BOOH) depended on the incubation time and oxidant concentration. [3H]Leucine incorporation was decreased to 20 and 47% of control values and TBARS were enhanced from the control value of 16.9 to 45.3 and 62.5 nmol/g of liver by incubation for 1 h with 1 mM BrCCl3 and t-BOOH, respectively. Following incubation, both protein synthesis damage and lipid peroxidation were decreased in control and oxidant-treated slices prepared from rats injected with 200 mg of DL-alpha-tocopherol/kg of body wt. Release of lactate dehydrogenase was not enhanced by oxidant treatment. Protein synthesis inhibitors reversibly decreased [3H]leucine incorporation, but the effect of oxidants on protein synthesis was irreversible. Cumene hydroperoxide and methyl ethyl ketone peroxide, but not hydrogen peroxide, damaged protein synthesis and induced lipid peroxidation. The ability of carbon tetrabromide, benzyl chloride, bromoform, bromobenzene, carbon tetrachloride, chloroform, dichloromethane, and bromochloromethane to inhibit protein synthesis was correlated with their ability to induce lipid peroxidation, and with their LD50. The results suggest that oxidant-induced lipid peroxidation and protein synthesis damage occurred concurrently, and that protein synthesis inhibition may be involved in cell injury or death mediated by free radicals.     

田螺科五种螺的核型研究

以早期胚胎细胞为材料,用火焰干燥法制片,对分布于我国湖北省武汉市近郊的常见田螺科(Viviparidae)五种螺的核型进行了分析。结果:两种圆田螺的染色体数和国外报道的同一属的种类的一致。而三种环棱螺的染色体数,则较国外报道的另两种的少得多。在铜锈环棱螺的核型中,其m组的第一对和sm组的第四对染色体上,具有明显的随体,出现频率甚高。     

中国鲤科鱼类染色体组型的研究 Ⅱ.鲴亚科四种鱼的染色体组型

鲴亚科(Xenocyprininae)鱼类多为中小型鱼类,常见于江河湖泊等较宽阔的水域中,我国长江、黑龙江、黄河及珠江诸流域皆有分布,共有10种,隶属4个属(伍献文等,1964)。迄今尚未见有该亚科鱼类染色体组型的研究报道。本文是对其中三属四种鱼的染色体组型的观察结果。这四种鱼是银鲴(Xenocypris argentea)、黄尾鲴(Xenocypris davidi)、细鳞斜颌鲴(Plagiognathops microlepis)和逆鱼(Acanthobrama simoni)。其中黄尾鲴和细鳞斜颌鲴均为新的淡水养殖鱼(沈德长等,1981;陈楚星,1979)。     

植物冷锻炼对于胁强敏感度的影响(英文)

前文由柑桔枝条在不同低温下、不同冷冻时间的电解质外渗测定,提出胁强(stress)、作用时间与胁变(strain)之间关系的数学模型。在这个模型中共有3个参数:屈服点温度(yield point temperature),胁强敏感度(stress sensitivity)和作用时间敏感度(sensitivity to duration),用以描述植物的抗性。抗性强的植物应表现为屈服点温度较低,胁强敏感度或者时间敏感度较低。为验证此数学模型,本工作以经冷锻炼与未经冷锻炼的盆栽柑桔枝条为材料,作不同温度与时间处理的电解质外渗率的测定,研究了冷锻炼对于上述3个参数的影响。发现胁强敏感度和屈服点温度受冷锻炼影响而下降,时间敏感度未表现明显变化。对于田间柑桔、油桐与毛竹的定期测定,在固定冷冻时间下,得到了类似于盆栽柑桔的结果。入冬时,植物抗冻性提高,3种植物都表现出下列两种变化:1.胁强敏感度的明显下降;2.屈服点温度和/或时间敏感度亦下降。开春时的变化则相反。胁强敏感度的变化与后一种变化有各自的规律,且因植物种类而不同。拐点胁强(stress at inflection point)具有与半致死温度(50％killing point temperature)不同的意义,它的变化是上述两种变化的综合结果。本试验结果表明,冷锻炼对于植物胁强敏感度有明显影响,用本数学模型的3个抗性指标描述     

Extremely short 20-33 nucleotide introns are the standard length in Paramecium tetraurelia.

Paramecium tetraurelia has the shortest known introns as its standard intron length. Sequenced introns vary between 20 and 33 nucleotides in length. The intron sequences were discovered in genomic sequences coding for a variety of different proteins, including phosphatases, kinases, and low-molecular weight GTP-binding proteins. All intron sequences begin with the conserved dinucleotide GT and end with the conserved dinucleotide AG. The sequences are more AT rich than the Paramecium coding sequences. The identified sequences were confirmed as introns by sequencing several cDNA fragments. We report here analysis of the characteristics of 50 separate introns, including size, base composition, and a consensus sequence.     

Use of recombinant interferon-α in Human Immunodeficiency Virus (HIV)-infected individuals

Rationale and objective Interferon alpha (IFN-) has anti-retroviral activity and is a possible HIV infection-limiting factor. The aim of this work is to prevent or delay disease progression in asymptomatic Human Immunodeficiency Virus (HIV) carriers.Design and interventions Recombinant IFN alpha-2b (3×10⁶ IU 3 times weekly) was compared. to no treatment (control) in a randomized trial. Endpoints were: (i) appearance of any CDC group IV symptoms and (ii) disease progression (which excluded shifts to group IVC2 or reversible IVA, or IVB). The trial lasted from October 1987 to February 1992.Setting The trial was performed at the Santiago de las Vegas sanatorium, a specialized institution for the care of HIV-infected and AIDS patients.Population Subjects were anti-HIV-1 seropositive, Western blot-confirmed, asymptomatic (CDC group II), or with generalized lymphadenopathies (CDC group III). The groups had 79 (control) and 71 (IFN) patients.Main results Long-term IFN- treatments significantly reduced the proportion of patients who shifted to any group IV (control: 46/79; IFN: 14/71;p<0.001) or developed AIDS (control: 27/79; IFN: 12/71;p<0.05). IFN also delayed progression to AIDS (95% confidence interval for 0.5 probability of progression) from 67–83 to 116–180 months after infection. The IFN group had significantly less opportunistic infections and non-infectious complications. CD4 cell count and hemoglobin decreased in the control but not in the IFN group. Fewer IFN-treated patients developed positive serum HIV antigen detection.Conclusion IFN alpha treatment during the early stages of infection seems to be beneficial to the patients.Abbreviations CI confidence interval - AIDS Acquired Immunodeficiency syndrome - HIV Human Immunodeficiency Virus - IFN Interferon - CDC Center for Disease Control (USA) - SD standard deviation     

Fluorescent detection-polymerase chain reaction (FD-PCR) assay on microwell plates as a screening test for salmonellas in foods

This study evaluates a polymerase chain reaction assay coupled with a fluorescent detection in microwell plates for salmonellas in food samples. Chelex 100-extracted cultures and bulk and processed food samples were used as templates for a PCR assay in microwell plates, with a primer pair that amplifies a 206 bp segment of IS 200 . The PCR products were then denatured by heat and transferred to CovaLink NH plates (Nunc) to which capture oligonucleotides were covalently bound. Hybridization was performed for 1 h at 55°C, the microwells were washed and an alkaline phosphatase-labelled probe, complementary of an internal sequence of the PCR product, was added. After stringent washes, 100 μl of 1 mmol 1^-1 AttoPhos^TM (JBL Scientific) was then added to the wells and the fluorescence measurement system (Millipore). The level of detection of the assay was as low as 1–10 cfu. A total of 172 food samples were tested, both by culture and FD-PCR. Of these 53 were culture positive and 119 culture negative. The sensitivity of the FD-PCR assay was 100% and the specificity was 90.1%. Positive and negative predictive values were 82.8 and 100%, respectively. Based on the results obtained in this study it appears that the FD-PCR. assay described here can be useful to screen a large number of food samples for contamination by salmonellas.     

微生物发酵法生产S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(S-adenosyl-l-methionine, SAM)广泛存在于生物体内,主要参与生物体内的转甲基过程、转硫过程及转氨丙基过程,具有重要的生理功能,其生产备受重视。目前SAM生产的研究主要集中于微生物发酵法,该方法与化学合成法和酶催化法相比,成本较低且更容易实现工业化生产。随着需求量的迅速增加,通过菌种改良提高SAM产量备受关注。当前SAM生产菌种改良的主要策略包括常规育种和代谢工程。本文综述了提高微生物生产SAM能力的近期研究进展并探讨了SAM生产中的瓶颈问题及解决方法,以期为进一步提高SAM产量提供思路。     

Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin

We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells.     

Chromium content in human milk,Cow's milk,and infant formulas

Chromium was measured by Electrothermal Atomic Absorption Spectrometry in human milk, cow's milk, and infant formulas. The mean levels found were 1.56, 0.83, and 4.84 (13%) μg/L, respectively. According to our data, the daily intake for the Spanish neonates is lower than the Recommended Dietary Allowances (RDAs) (10–40 μg/d) for this element.