Molecular changes in cell surface membranes resulting from trypsinization of sarcoma 180 tumor cells

Sarcoma-180 tumor cells in culture or grown as an ascites form in the CD-1 mouse have been subjected to mild trypsinization procedures in order to study morphological and molecular changes resulting from proteolysis. The cells attached to a substratum become rounded within 20 min and most undergo cell division, but they do not detach from the substratum. Removal of trypsin permits the cells to go back to their original spindle shape over an 8–20 h period.Surface membranes were isolated from trypsinized ascites and cultured cells and subjected to dodecyl sulfate-acrylamide gel electrophoresis. Both cell types showed the same two kinds of changes in electrophoretic patterns. First, there was a loss of glycoproteins from both cell types, even though they show different complements of cell surface glycoproteins. Second, there is a loss of high molecular weight polypeptides, which have previously been suggested to play a role in membrane stabilization and cell shape. These results further implicate these polypeptides in the control of cell morphology and offer circumstantial evidence for transmembrane interactions of surface glycoproteins with the high molecular weight polypeptides as a factor in controlling cell morphology.     

The surface morphology of normal and malignant rat liver epithelial cells in culture

Summary A direct comparison has been made between normal parenchymal cells cultured from rat liver and malignant cells from both a rat liver tumor and a spontaneously transformed line derived from the parent rat culture. In all nondividing cells there was a 3- to 5-fold increase in the population of surface microvilli on the malignant cells compared to the normal cells. Notable variations in overall morphology were also observed when cells were incubated in arginine-deficient medium. During the course of this work T. D. Allen and P. T. Iype were supported by grants from the Medical Research Council and Cancer Research Campaign, and M. J. Murphy, Jr. was supported by a Special Fellowship of the Leukemia Society of America, Inc. and the Jean Shaland Fund.     

Studies on the binary and ternary complexes formed by a neurospora glutamate dehydrogenase and its substrates

The NADP⁺ specific glutamate dehydrogenase from wild-type $\text{Neurospora crassa}$ forms a stable binary complex with NADPH. This can combine with L-glutamate, α-ketoglutarate or the substrate analogue D-glutamate to form ternary complexes which can be distinguished by their different fluorescence properties. The affinity of the enzyme for NADPH diminishes with increases in pH or ionic strength of the solution. Experimental data obtained using modified glutamate dehydrogenases from mutant strains of $\text{N. crassa}$ suggest that the reduced-coenzyme binding sites observed fluorimetrically are the same as those observed by enzyme kinetics.     

Antioxidant Activity of New Sulphur- and Selenium-Containing Analogues of Potassium Phenosan against H2O2-Induced Cytotoxicity in Tumour Cells

Among known phenolic antioxidants, the overwhelming majority of compounds have lipophilic properties and the number of known water-soluble compounds is very small. The list of hydrophilic phenolic antioxidants can be expanded via the synthesis of a structurally related series of polyfunctional compounds for further research on their biological activity in vitro. New sulphur- and selenium-containing analogues of antioxidant potassium phenosan were synthesised. In vitro cytotoxicity and cytostaticity as well as antioxidant activity against H₂O₂-induced cytotoxicity to human cell lines (HepG2, Hep-2 and MCF-7) were investigated by high-content analysis. A selenium-containing analogue showed higher biological activity than did a sulphur-containing one. As compared to the activity of potassium phenosan, the selenium-containing analogue had a cell line-dependent antioxidant effect against H₂O₂-induced cytotoxicity: comparable in HepG2 cells and greater in Hep-2 cells. The selenium-containing analogue significantly increased the death of MCF-7 cells at concentrations above 50 µM. The sulphur-containing analogue has lower biological activity as compared to potassium phenosan and the selenium-containing analogue.     

综述与专论: 针对严重急性呼吸综合征冠状病毒2变异株Omicron的疫苗研究进展

2021年底,严重急性呼吸综合征冠状病毒2 Omicron变异株迅速取代Delta突变株在世界范围内广泛流行,其S蛋白具有36个位点突变,导致致病力和传播力发生明显变化,并且具备了免疫逃逸的能力。疫苗接种是目前疫情防控最普适的手段,研究发现,现有疫苗针对Omicron突变株的保护效果明显下降。新的免疫策略或特异性疫苗/多价疫苗针对Omicron有效性的评估均需要动物模型的支撑。在实验室条件下,利用动物模型进行活病毒攻击实验,是在体内验证保护性中和抗体、疫苗有效性的关键技术手段,本文将从动物模型方向综述国内外针对Omicron变异株的疫苗研究进展。     

Kinetic Monte Carlo simulation for the striation distribution of void defects in Czochralski silicon growth

Unique crystal-originated pit (COP) distribution, similar to a striation pattern, is well matched with the oxygen profile in experimental analysis. It shows the strong relationship between oxygen concentration and COP distribution. In this paper, we study the generation of void defects and the relationship between interstitial oxygen and vacancy using the kinetic lattice Monte Carlo (KLMC) method. The KLMC method has been applied extensively in various forms to the study of micro-defects in silicon wafers. It explained well the formation of void defects such as vacancy–oxygen complex and vacancy–vacancy complex. The formation of clusters is strongly affected by oxygen concentration, which showed the relationship between COP distribution and oxygen concentration. The unique COP distribution could be correctly explained with KLMC results, and this kind of meso-scale results has not yet been reported.     

Reconfiguration of a Multi-oscillator Network by Light in the Drosophila Circadian Clock

1. Download high-res image (157KB)
2. Download full-size image

     

原癌基因ras在玉米中同源序列的检出及其荧光原位杂交定位

原癌基因ｒａｓ是动物中抑制细胞凋亡的重要基因之一。以人的ｒａｓ基因为探针,通过Ｓｏｕｔｈｅｒｎ杂交技术,确证玉米和水稻中均含有ｒａｓ基因的同源序列;同时,运用荧光原位杂交技术,首次对ｒａｓ基因在玉米中的同源序列进行了定位。结果表明：ｒａｓ探针在第２号和第７号染色体上均检出了杂交信号,信号检出率分别为１０．８５％和１４．１５％,杂交信号与着丝粒的百分距离分别为 ５４．９２± １．９０和 ９４．６２± ２．７７。上述研究结果为植物细胞凋亡的进一步研究提供了线索和帮助。     

Study on fibroin heavy chain of the silkwormBombyx mori by fluorescencein situ hybridization (FISH)

The sericulture industry plays a very important role in our national economy. Silkworm (Bombyx mori) is always regarded as a model animal and biological reactor. There have been detailed studies on the structure, expression and control and molecular evolution of silk genes. However, few, if any, reports are available on the localization of structural genes in silkworm by molecular cytogenetics. The present experiment has tentatively localized theFib-H gene at the distal end of the 25th linkage group, namely at the 25-0.0 position, and verified thatFib-H has only one locus, thus providing a temporary solution to the problem about its localization.