Wild-type p53 restores cell cycle control and inhibits gene amplification in cells with mutant p53 alleles.

Loss of cell cycle control and acquisition of chromosomal rearrangements such as gene amplification often occur during tumor progression, suggesting that they may be correlated. We show here that the wild-type p53 allele is lost when fibroblasts from patients with the Li-Fraumeni syndrome (LFS) are passaged in vitro. Normal and LFS cells containing wild-type p53 arrested in G1 when challenged with the uridine biosynthesis inhibitor PALA and did not undergo PALA-selected gene amplification. The converse occurred in cells lacking wild-type p53 expression. Expression of wild-type p53 in transformants of immortal and tumor cells containing mutant p53 alleles restored G1 control and reduced the frequency of gene amplification to undetectable levels. These studies reveal that p53 contributes to a metabolically regulated G1 check-point, and they provide a model for understanding how abnormal cell cycle progression leads to the genetic rearrangements involved in tumor progression.     

Formation ofα,ω-dodecanedioic acid andα,ω-tridecanedioic acid from different substrates by immobilized cells of a mutant ofCandida tropicalis

Summary The metabolic formation of either,-dodecanedioic acid or,-tridecanedioic acid from the individual n-alkane, n-alcohol, n-monoacid and,-diol with corresponding carbon chain length using K-carrageenan entrapped mutants S76 ofCandida tropicalis was studied. The immobilized cells of S76 could also directly produce-hydroxy acid and,-dioic acid from,-diol. With n-alcohol and n-monoacid as substrate, the amount of-hydroxy acid and,-dioic acid produced was also a function of the incubation time.The results demonstrated that in the immobilized cells of S76 the formation of,-dioic acid from n-alcohol can also run both via n-monoacid and via,-diol as well as in the normal cells of S76.     

A new metabolic pathway from n-dodecane to α, ω-dodecanedioic acid in a mutant of Candida tropicalis

Summary The metabolic formation of ,-dodecanedioic acid via ,-dodecanediol from n-dodecane using a mutant S76 of Candida tropicalis was studied.It was found that resting cells of S76 produce ,-dodecanediol from n-dodecane. This intermediate was identified by different analytical methods. With n-dodecanol as substrate the quantitative changes in the concentrations of ,-dodecanediol as well as other intermediates, e.g. monoacid, -hydroxy acid and ,-dioic acid produced by resting cells of S76 for different periods of time were determined. With ,-dodecanediol as the sole carbon source, quantitative changes of -hydroxy acid and ,-dioic acid produced by S76 were also recorded.The results confirm the existence of a new metabolic pathway via ,-diol in the course of ,-dioic acid formation from n-alkane in the mutant S76 of C. tropicalis.     

Purification and structural properties of gelsolin, a Ca2+-activated regulatory protein of macrophages

We describe the purification procedure and some of the physiochemical properties of gelsolin, a major Ca2+-dependent regulatory protein of actin gel-sol transformation in rabbit lung macrophages. Gelsolin accounts for the majority of Ca2+ control of actin gelation in macrophage extracts. It is a single polypeptide chain with an average molecular weight of 91,000 a Stokes radius of 44 A, a sedimentation coefficient (s20(0),w) of 4.9 S, an isoelectric point of 6.1, and a frictional ratio of 1.43. Gelsolin binds 2 mol of Ca2+ with high affinity (Ka 1.09 X 10(6) M-1) in the presence of 0.1 M KCl and 2 mM MgCl2.     

Reconstituted low density lipoprotein: A vehicle for the delivery of hydrophobic fluorescent probes to cells

Previous studies have shown that the cholesteryl ester core of plasma low density lipoprotein (LDL) can be extracted with heptane and replaced with a variety of hydrophobic molecules. In the present report we use this reconstitution technique to incorporate two fluorescent probes, 3-pyrenemethyl-23, 24-dinor-5-cholen-22-oate-3β-yl oleate (PMCA oleate) and dioleyl fluorescein, into heptane-extracted LDL. Both fluorescent lipoprotein preparations were shown to be useful probes for visualizing the receptor-mediated endocytosis of LDL in cultured human fibroblasts. When normal fibroblasts were incubated at 37°C with either of the fluorescent LDL preparations, fluorescent granules accumulated in the perinuclear region of the cell. In contrast, fibroblasts from patients with the homozygous form of familial hypercholesterolemia (FH) that lack functional LDL receptors did not accumulate visible fluorescent granules when incubated with the fluorescent reconstituted LDL. A fluorescence-activated cell sorter was used to quantify the fluorescence intensity of individual cells that had been incubated with LDL reconstituted with dioleyl fluorescein. With this technique a population of normal fibroblasts could be distinguished from a population of FH fibroblasts. The current studies demonstrate the feasibility of using fluorescent reconstituted LDL in conjunction with the cell sorter to isolate mutant cells lacking functional LDL receptors.     

长山群岛海域真核微藻粒级结构及扇贝摄食选择性

采用高通量测序-分子鉴定分级技术于2019年对长山群岛全海域真核微藻粒级结构进行了研究。结果发现,春季以中（47%）、小粒级（41%）为主,夏季以小（39%）、大粒级（38%）为主,秋季以大粒级（60%）为主,春、夏、秋季小、中、大粒级微藻比例为42：47：11、39：23：38、22：18：60。小粒级微藻优势种为细小微胞藻（Micromonas pusilla）、融合微胞藻（Micromonas commoda）和金牛微球藻（Ostreococcus tauri）,中粒级微藻优势种为剧毒卡尔藻（Karlodinium veneficum）、大粒级微藻优势种为柔弱几内亚藻（Guinardia delicatula）、平野亚历山大藻（Alexandrium hiranoi）、多纹膝沟藻（Gonyaulax polygramma）,综合整个真核微藻群落,春季由中粒径的剧毒卡尔藻占据优势（23.9%）,夏季由大粒径的平野亚历山大藻占据优势（29.4%）,秋季由大粒径的多纹膝沟藻占据优势（66.8%）,有毒甲藻在该海域中占有绝对优势,贝毒累积风险较高,小粒径微藻中金牛微球藻和抑食金球藻曾在渤海引发褐潮,潜在威胁该海域贝类养殖业。虾夷扇贝对小粒级和大粒级微藻的选择性较低,对中粒级微藻的选择性较高,尤其对水体中优势种剧毒卡尔藻一直表现出主动选择。光学需氧量、无机氮、溶解氧、石油类及部分重金属Cd、As、Hg影响着整个长山群岛海域真核微藻粒级结构时空演变。     

一株兔源A型多杀性巴氏杆菌的分离鉴定和全基因组测序及分析

【背景】多杀性巴氏杆菌可导致猪肺疫、牛出血性败血症和兔出血性败血症等多种疾病,严重威胁多种动物畜牧养殖业的健康发展。【目的】重庆某兔场送检一批病死兔,为研究其病原和治疗方法,对病原进行了微生物分离和全基因组测序分析。【方法】从2022年重庆某兔场送检兔病料中进行细菌分离纯化、生化试验、16S rRNA基因鉴定、荚膜血清型分型、药敏试验和毒力基因检测,同时通过全基因组测序结果进行毒力、耐药基因注释和遗传进化等分子生物学信息分析。【结果】该菌为兔源A:ST74多杀性巴氏杆菌,命名为LXSS001,基因组序列上传到NCBI数据库(登录号为CP119523.1),药敏试验显示该菌对四环素、杆菌肽、复方新诺明和磺胺异恶唑耐药,对头孢噻肟、头孢哌酮和丁胺卡那等药物敏感。全基因组长度为2 480 671 bp,并注释到了58个毒力基因和9类药物的靶向抗药基因。通过联合建树表明其与3480株一致性最高。【结论】本研究完成了一株A型多杀性巴氏杆菌的分离鉴定和全基因组测序,并揭示了其与国内外其他分离株的进化关系,为多杀性巴氏杆菌的后续研究提供了参考依据。     

Influence of nitrogen sources on the tolerance of Lacticaseibacillus rhamnosus to heat stress and oxidative stress

It has been found that 32 genes related to nitrogen source metabolism in Lacticaseibacillus rhamnosus are downregulated under both heat stress and oxidative stress. In this study, the influence of different nitrogen sources within the growth medium on the tolerance of L. rhamnosus to heat stress and oxidative stress was investigated. Tryptone-free MRS was found to enhance the tolerance of L. rhamnosus hsryfm 1301 to heat stress and oxidative stress during the whole growth period, and this result was universal for all L. rhamnosus species analyzed. The strongest strengthening effect occurred when the OD₆₀₀ value reached 2.0, at which the survival rates under heat stress and oxidative stress increased 130-fold and 40-fold, respectively. After supplementing phenylalanine, isoleucine, glutamate, valine, histidine, or tryptophan into the tryptone-free MRS, the tolerance of L. rhamnosus to heat stress and oxidative stress exhibited a sharp drop. The spray drying survival rate of L. rhamnosus hsryfm 1301 cultured in the tryptone-free MRS rose to 75% (from 30%), and the spray dried powder also performed better in the experimentally simulated gastrointestinal digestion. These results showed that decreasing the intake of amino acids is an important mechanism for L. rhamnosus to tolerate heat stress and oxidative stress. When L. rhamnosus is cultured for spray drying, the concentration of the nitrogen source''s components should be an important consideration.     

全球气候治理新进展——区域碳排放权分配研究综述

碳排放权作为稀缺的公共资源,其实质是一种新型发展权。科学合理分配有限的碳排放权对实现《巴黎协定》温控目标至关重要。从原则、方法、尺度与方案等维度对碳排放权分配的文献成果进行了系统梳理与归纳。研究表明,国内外学者大多基于公平性和效率性原则探索碳排放权分配;分配方法分为指标法、博弈论法、数据包络分析法和综合法等,各有利弊和适用条件;分配尺度大多涉及国际和区际两个层面,前者由于各国不同的利益诉求较难形成共识性方案,后者主要关注省际分配,更小尺度的研究相对较少。未来碳排放权分配研究趋向于多原则兼顾、多方法联用,涵盖国际、省际、市际及行业、企业等不同尺度。本研究可为制定科学合理的碳排放权分配方案提供理论依据,为我国更为积极有效地参与全球气候治理提供决策参考。