Structural correlates of cellular tumorigenicity and anchorage independence in transformed fibroblasts

The ability on nonhematopoietic cells to proliferate in vitro without attachment to a solid surface (anchorage independence) is known to be highly correlated with their ability to form tumors in nude mice. Transformed cells in vitro frequently also show less organization of the intracellular actin-containing microfilament bundles and less cell-surface fibronectin compared to normal cells. We have examined whether the loss of the anchorage requirement for growth is related to either of these structural changes in the cellular cytoskeleton. Our approach was to select a series of subclones from a nontransformed Syrian hamster fibroblast line, NIL8, for the acquisition of either anchorage independence in vitro or tumorigenicity in nude mice. These subclones were then examined for concomitant changes in the cytoskeletal structures. We found that anchorage independence, decreased actin cable organization, and tumorigenicity in nude mice were coordinately induced in both the in vitro- and in vivo-selected subclones, whereas the loss of fibronectin was not consistently coinduced with these three markers. These results suggest that the transformation-associated decrease in actin cable organization in this type of cell enhances the ability to grow without anchorage in vitro and to form tumors in vivo.     

Interaction of metal ions with polynucleotides and related compounds. XXII. Effect of divalent metal ions on the conformational changes of polyribonucleotides

Changes in the conformation of poly(G), poly(C), poly(U), and poly(I) in the presence of divalent metal ions Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺, and Zn²⁺ have been measured by means of ORD and u.v. spectra. Mg²⁺ and Ca²⁺ ions stabilize helical structures of all the polynucleotides very effectively at concentrations several orders of magnitude lower than the effective concentration of Na⁺ion. Cu²⁺ and Cd²⁺ destabilize the helical structure of polynucleotides to form random coils. Zn²⁺, Ni²⁺, Co²⁺, and Mn²⁺ions do not behave in such a clear-cut manner: they selectively stabilize some ordered structures, while destabilizing others, depending on the ligand strength of the nucleotide base as well as the preferred conformation of that polynucleotide.     

鱼类染色体G—显带的Brd U—BSG方法及白鲢G—带模式图的初步建立

本文报道了一种显示鱼类染色体G-带的BrdU-BsG方法。采用肾细胞短期培养,收获前12小时加入BrdU,使终浓度为10μg/ml。制片经HCl、Ba(OH)_2处理,4×SSC温育。Giemsa染色,显示出白鲢的G-带。其带纹细致清晰,一个细胞的单倍染色体上显示带纹达200条以上,是目前已报道的鱼类多重带中带纹最多的,且反差明显,带纹有特征性,结果较稳定。根据实验结果初步建立了白鲢的G-带模式图。     

Detection of IgG and IgM antibodies with ELISA technique in human trichomoniasis

The direct wet mount examination of vaginal secretion, widely applied for the diagnosis of Trichomonas vaginalis infection in woman patients, is rapid and economical, however, the sensitivity of this technique is not so high. In this study enzyme-linked immunosorbent assay (ELISA) was employed for the detection of serum anti-T. vaginalis IgG and IgM antibodies from 30 vaginal trichomoniasis patients and 30 non-infected healthy persons. The results were as follows: 1. Serum ELISA-IgG value was 0.37 +/- 0.134 (Mean +/- S.D.) in vaginal trichomoniasis patients and 0.21 +/- 0.054 in healthy controls (p less than 0.005), and the sensitivity and specificity of ELISA for serum IgG antibody were 70.0% and 96.7%, respectively. 2. Serum ELISA-IgM value was 0.33 +/- 0.177 (Mean +/- S.D.) in vaginal trichomoniasis patients and 0.11 +/- 0.051 in healthy controls (p less than 0.005), and the sensitivity and specificity of ELISA for serum IgM antibody were 70.0% and 96.7%, respectively. 3. The ELISA-IgG values showed a significant correlation with ELISA-IgM values (r = 0.77, p less than 0.005). With above results, it is assumed that ELISA is a reliable method for the diagnosis of T. vaginalis infection and simultaneous measurement of serum IgG and IgM with this technique is recommended.     

Assembly and disassembly of brain tubulin is affected by high ammonia levels

Rats were fed a diet containing ammonium for up to 6 months. High ammonia levels were attained in brain. The amount of polymerized tubulin in microtubules increased, while the amount of free tubulin remained unchanged. Polymerization of tubulin from brain of ammonium fed rats (30 min, 37°C) was approximately 60% of control. Depolymerization of the microtubules was also affected and took approximately 3 times longer than in controls. These results indicate that both assembly and disassembly of tubulin in brain are impaired by high ammonia levels. Interestingly, the amount of microtubule-associated proteins was not affected.     

A protein-free diet changes synaptosomal membrane fluidity and tyrosine and glutamate transport

Synaptosomes were isolated from cerebrums of rats fed standard (20% protein) or protein-free diets for 30 days. Arrhenius plots of their (Na⁺/K⁺)ATPase activities revealed a transition temperature of 25.5°C for control rats and 23.4°C for rats on protein-free diet, indicating that the latter increases synaptosomal membrane fluidity. The only change observed in the composition of the synaptosomal membranes was a 26% decrease of sialic acid. In synaptosomes from rats on protein-free diet the uptake of tyrosine was slightly reduced while that of glutamate was not affected. However, the exit of glutamate was reduced.