Cell adhesion to substratum and activation of tyrosine kinases are essentially required for G1/S phase transition in BALB/c 3T3 fibroblasts

AbstractCell adhesion to substratum and activation of tyrosine kinases are essential for the progression of cell cycle through G1 phase in mammalian cells. The kinetic studies of mouse BALB/c 3T3 fibroblasts showed that serum was no longer required for the progression of G1/S phase transition. In contrast, cell adhesion was essentially required in late GI phase, especially at the period of G1/S transition. Among the kinase inhibitors used to elucidate the signal transduction caused by cell adhesion, tyrosine kinase inhibitors, genistein and herbimycin A, blocked the G1/S transition most effectively when cells were exposed to the inhibitors at the period of GI/S transition. Cell adhesion was not critically required for cells to undergo DNA synthesis once they had passed the G1/S boundary, and the effects of tyrosine kinase inhibitors on the progression of S phase were also not critical. The expressions of histone H2B and dihydrofolate reductase (DHFR) genes (S phase specific genes) and also the transcription factor E2F-1 gene (an activator of DHFR gene) were suppressed when cells were cultured without adhesion or exposed to the tyrosine kinase inhibitors. These results suggest that cell adhesion to substratum plays an important role in the G1/S phase transition of mouse BALB/c 3T3 fibroblasts through the activation of tyrosine kinases other than growth factor receptor-tyrosine kinases

Simulation for field emission images of micrometer-long SWCNTs

The electron distribution of open-ended single-walled carbon nanotubes with chirality indexes (7,0) and (5,5) in the field emission conditions was calculated via a multi-scaled algorithm. The field emission images were produced numerically. It was found that the emission patterns change with the applied macroscopic field. Especially, the symmetry of the emission pattern of the (7,0) carbon nanotube is breaking in the lower field but the breaking is less obvious in the higher field. The enlargement factor increases with the applied macroscopic field.Comment: 8 pages, 4 figure

Immunological quantitation of tyrosinase from wild-type and albino mutant mice

AbstractThe relationship between gene dosage, enzyme activity, and level of immunologically cross-reacting material (CRM) was examined in mammalian tyrosinase (EC 1.14.18.1) by rocket immunoelectrophoresis. Skin extracts from mice heterozygous (C/c) and homozygous (c/c) for the albino locus contain 46% and 0% of CRM, respectively, as compared with wild-type (C/C) animals. Enzyme activity and CRM level were directly proportional in these genotypes, suggesting that the albino locus controls the quantity of tyrosinase produced in melanocytes

Влияние состава газовой среды на параметры упрочнения стали при азотировании в тлеющем разряде

В работе были исследованы процессы азотирования стальных деталей машиностроения в плазме тлеющего разряда при замене традиционного аммиака на смесь газов, состоящую из азота, аргона и метана. Проведено сравнение параметров азотированных слоев в зависимости от состава рабочей среды и длительности обработки. Оценены технологические параметры и возможности применения метода в реальном производстве.In the work, the processes of nitriding of steel parts of machine building in a glow discharge plasma were investigated when traditional ammonia was replaced by a mixture of gases consist of nitrogen, argon and methane. The parameters of the nitrided layers are compared depending on the composition of the working environment and the processing time. The technological parameters and possibilities of application of the method in real production are estimated

Valley spin polarization by using the extraordinary Rashba effect on silicon

The addition of the valley degree of freedom to a two-dimensional spin-polarized electronic system provides the opportunity to multiply the functionality of next-generation devices. So far, however, such devices have not been realized due to the difficulty to polarize the valleys, which is an indispensable step to activate this degree of freedom. Here we show the formation of 100% spin-polarized valleys by a simple and easy way using the Rashba effect on a system with C-3 symmetry. This polarization, which is much higher than those in ordinary Rashba systems, results in the valleys acting as filters that can suppress the backscattering of spin-charge. The present system is formed on a silicon substrate, and therefore opens a new avenue towards the realization of silicon spintronic devices with high efficiency.X114334Nsciescopu

Measurements of the Total Reaction Cross Section in 12C, 13C, 14N, 15N, 16O + 28Si Systems

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Expression of a Cross-reactive Antigen on the Surface of Human Carcinomas Overproducing Epidermal Growth Factor Receptors Shared with RSV induced Tumors

Analysis based on the complement-dependent cytotoxicity (CDC) assays using syngeneic antiserum against a Rous sarcoma virus (RSV)-induced mouse tumor (CSA1M) showed that a cross-reactive antigen with a common tumor-associated cell surface antigen (TASA) of RSV-induced mouse tumors was shared with two human tumors A431 and MDA-468 overexpressing epidermal growth factor receptors (EGFRs). The TASA, however, was not expressed on four human choriocarcinomas, a human lung cancer A2182, and human embryo fibroblasts HEF. Immunofluorescent studies demonstrated that A431 did not express a src gene product detected by rabbit anti-pp60V-src serum. Two variant clones derived from A431 reducing number of EGFRs (cl-15 and cl-16) had almost the same growth rate and expression of transferrin receptor (Tf-R) in comparison with parental A431 cells. These clones, however, decreased the expression of the TASA. Furthermore, CDC assays and enzyme-linked immunosorbent assays (ELISA) revealed that A431 reduced the expression of the TASA by pretreatment of EGF, but not with insulin. A truncated form corresponding to extracellular domain of the EGFR blocked the cytotoxicity of anti-CSA1M serum to A431 and RSV-induced tumor cells. All these findings indicate a close association between a cross-reactive antigen with the TASA of RSV-induced tumors and the EGFR expression

Expression of ras Oncogene p21 Product in Malignant and Benign Lesions and Normal Mucosae of the Stomach in China

Expression of c-ras oncogene was analyzed in 75 cases of carcinomas, 38 benign lesions and 22 normal mucosae of the stomach in Chinese subjects by use of the monoclonal antibody rp28, which reacts to the c-Ha-ras and c-Ki-ras p21 products. The incidence of p21 positive cases (more than 20% of total cells stained by rp28) was 90.7% in gastric carcinomas, 10.5% in benign gastric lesions and 4.5% in normal mucosae. While 34/75 gastric carcinomas contained strongly rp28-reactive (+ +) cells, none of the benign lesions or normal mucosae did. The mean percentage of rp28 reactive (+ or ++) cells in each group was 52.2% in gastric carcinomas, 6.3% in benign lesions and 2.3% in normal mucosae. These indicate that ras p21 expression is significantly high in the gas-tric carcinomas compared to the benign lesions and normal mucosae of the stom-ach. Tests of tubular adenocarcinomas with different degrees of differentiation showed significantly higher amounts of p21 product in well differentiated (71.7%) and moderately differentiated (67.3%) samples than in poorly differentiated adenocarcinomas (40.9%), which contained more, in tern, than mucinous adenocarcinomas (39.2%) and undifferentiated carcinomas (27.5%). This sug-gests that Ha- and/or Ki-ras p21 expression may have some roles in the mainte-nance of the glandular structure in gastric carcinomas

Calibration of Large Volume Neutron Detector

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Effect of ball-milling time on mechanical and magnetic properties of carbon nanotube reinforced FeCo alloy composites

Carbon nanotubes (CNTs) reinforced FeCo alloys were produced by high energy ball-milling and spark plasma sintering (SPS). CNTs distribution in the FeCo alloy was gradually improved as ball-milling time increased, with a uniform dispersion achieved after 6 h ball-milling. Tensile tests demonstrated that, as the ball-milling time increased, the yield strength increased in the composites; a maximum 50% relative increase in tensile strength due to the addition of CNTs was achieved after 1 h ball-milling, which then decreased with further ball-milling. The elongation to fracture was significantly increased after 1 h ball-milling and then decreased with further ball-milling. SEM results show a patch of dimples in the fracture surface of the composite, indicating improved ductility due to CNTs. The coercivity was increased with increased ball-milling time, while the saturation induction showed a peak value after 1 h of ball-milling and then decreased with further ball-milling. Raman spectra of the composite indicated that no serious damage had been imparted to the CNTs during ball-milling