A modified method of UDS detection in vitro suitable for screening the DNA-damaging effects of chemicals

The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test.     

天冬酰胺酶及PEG_2-天冬酰胺酶对L-天冬酰胺、谷氨酰胺亲和性的研究

本文报导了天冬酰胺酶及PEG_2-天冬酰胺酶对废物L-天冬酰胺、谷氨酰胺亲和性的研究,结果表明:PEG_2-天冬酰胺酶对谷氨酰胺的亲和性明显强于天冬酰胺酶(Km值分别为7.35×10~(-3)mol/L和7.14×10~(-2)mol/L),对天冬酰胺的亲和性略强于天冬酰胺酶(Km值分别为2.9×10~(-5)mol/L和4.0×10~(-5)mol/L)。天冬酰胺酶和PEG_2-天冬酰胺酶的CD光谱表明:天冬酰胺和谷氨酰胺对天冬酰胺酶和PEG_2-天冬酰胺酶的构象影响较大,但天冬酰胺酶和PEG_2-天冬酰胺酶的构象变化趋势有明显的不同。     

下肢长骨骨重的非对称性

本文测量82副中国成年下股长骨即股骨,胫骨和腓骨的重量,在两侧骨重相差>1％时,则股骨、胫骨和腓骨及其三骨总重均以非对称性为多,均具有非常显著性差异(P<0.001)。除腓骨重具有明显侧别差异外,其余无显著性侧别差异,对腓骨侧差解释为:①腓骨主要机能是肌的附着,而下肢对踢和足趾取物具有明显的侧别差异;②以两侧骨重相差>1％时为非对称性的标准,由于腓骨绝对重量较小,在两侧相差<0.5克时即多属非对称性。     

钐在小鼠肝脏细胞中的动态观察

It is generally considered that the rare earth compounds are plasma membrane-impermeable, thus affecting the cells only on their surface. Recently, we found that after repeated injections to mice of large dose of samarium trichloride, a soluble compound of rare earth, samarium aggregates appeared in Kupffer cells and hepatocytes of liver. In this study, we aimed at observing the route by which samarium enters the liver cells and the process of the formation of samarium aggregates. Samarium trichloride was given to Swiss mice at one dose of 70 mg/kg intravenously. Thereafter, at different intervals from 15 min to 48 h after the injection, the samarium in liver was traced dynamically by electron microscopy and X ray microanalysis. From 15 min to 2 h both Kupffer cells and hepatocytes endocytosed samarium-containing particles and formed phagosomes, in which the ingested particles were progressively concentrated. Besides, the small phagosomes fused with each other. Phagocytosis was especially active in Kupffer cells. During the 4 h to 24 h many Kupffer cells were degenerated and broken. In hepatocytes the phagosomes gathered mostly around the bile canaliculi. Groups of highly electron-dense particles were found in the lumen of bile canaliculi, implying the excretion of samarium by bile. At the 48 h, the samarium-containing phagosomies were found still in both kinds of cells in the liver.     

Simultaneous convective and diffusive mass transfers in a hemodialyser

The mass transfer in a hemodialyser in the presence of combined dialysis and ultrafiltration has been calculated by integration of mass fluxes across the boundary layers in blood and dialysate phase taking into account the partial rejection of solute as well as changes in local blood flow and ultrafiltration flux along the membrane. Clearances of creatinin, vitamin B12, and myoglobin have been calculated as a function of blood and ultrafiltrate flow rate and were found to be in good agreement with in vitro measurements. The data suggest the following empirical correlation for the hemodiafiltration clearance.     

云南的金鹬虻属五新种（双翅目：鹬虻科）

本文报道了在云南发现的金鹬虻属五新种,并与已发表种作了必要的比较。     

灯光诱虫在森林—鱼塘复合生态系统中的作用

昆虫是森林生态系统中的重要组成部分。由于森林中枯枝落叶较多,生境复杂,为昆虫提供了良好的繁殖和栖息场所;因而在森林中昆虫的种类多,数量大。大多数昆虫都以森林     

高温厌氧条件下纤维素的直接乙醇发酵

本文介绍了出分解纤维素的嗜热厌氧菌Clostridium celluloflavus sp.nov.直接发酵纤维素产乙醇的初步研究、发酵于60℃下进仃,其主要产物为乙醇、乙酸、氢气和二氧化碳。文中介绍了间歇发酵的若干特征与影响发酵的因素,1％纤维素发酵至120小时,大约有70％纤维素被分解;乙醇的转化率约为0.36g/g降解纤维素;发酵液中乙醇浓度达到56至61mM。发酵中乙醇与乙酸浓度的比值因发酵时间与其它发酵条件的不同而不同。     

Oligomerization of uridine phosphorimidazolides on montmorillonite: A model for the prebiotic synthesis of rna on minerals

The 5-phosphorimidazolide of uridine reacts on Na⁺-montmorillonite 22A in aqueous solution to give oligomers as long as 7 mers. The maximum chain length increases to 9 mers and the overall oligomer yield increases when 9:1 ImpU, A⁵ ppA mixtures react under the same conditions. The oligomer yield and maximum chain length decreases with the structure of the added pyrophosphate in the order A⁵ ppA>A⁵ ppU>U⁵ ppU. Structure analysis of individual oligomer fractions was performed by selective enzymatic hydrolyses followed by HPLC analysis of the products. The regioselectivity for 3,5-bond formation is 80–90% in the 9:1 ImpU, A⁵ ppA reaction, a percentage comparable to that observed in the 9:1 ImpA, A⁵ ppA reaction. Oligomerization of ImpU is inhibited by addition of dA⁵ ppdA, and MeppA. No oligomers containing A⁵ ppU were products of the 9:1 ImpU, A⁵ ppA reaction, a finding consistent with the simple addition of the ImpU to the A⁵ ppA and not the rearrangement of an ImpU-A⁵ ppA adduct. Concentrations of lysine or arginine which were close to that of the ImpU did not inhibit oligomer formation. Treatment of Na⁺-montmorillonite with 1 M arginine yielded arginine-montmorillonite, an amino acid-mineral adduct which did not catalyze ImpU oligomerization. Neither the 4–9 mers formed in the 9:1 ImpU, A⁵ ppA reaction nor the 4–9 mers formed by the base hydrolysis of poly(U) served as templates for the formation of oligo(A)s.