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1.
Masa-aki Sato 《Biological cybernetics》1990,62(3):237-241
A new learning algorithm is described for a general class of recurrent analog neural networks which ultimately settle down to a steady state. Recently, Pineda (Pineda 1987; Almeida 1987; Ikeda et al. 1988) has introduced a learning rule for the recurrent net in which the connection weights are adjusted so that the distance between the stable outputs of the current system and the desired outputs will be maximally decreased. In this method, many cycles are needed in order to get a target system. In each cycle, the recurrent net is run until it reaches a stable state. After that, the weight change is calculated by using a linearized recurrent net which receives the current error of the system as a bias input. In the new algorithm the weights are changed so that the total error of neuron outputs over the entire trajectory is minimized. The weights are adjusted in real time when the network is running. In this method, the trajectory to the target system can be controlled, whereas Pineda's algorithm only controls the position of the fixed point. The relation to the back propagation method (Hinton et al. 1986) is also discussed. 相似文献
2.
Types,rates, origin and expressivity of chromosome mutations involving 13q14 in retinoblastoma patients 总被引:7,自引:2,他引:5
Summary A cytogenetic survey of 200 retinoblastoma (Rb) patients revealed that approximately 8.5% of the fresh germinal mutations were microscopically detectable chromosome mutations, either interstitial deletions or rearrangements, involving 13q14. They showed a strong bias toward paternal origin, indicating a significant contribution of errors in paternal meiotic processes. The incidence of patients with Rb due to such chromosome mutations was estimated to be 1.9 x 10-6 of live births. Age-specific incidence of Rb tumors suggested that the Rb mutations by such chromosomal mechanisms had a lower carcinogenic potential, as indicated by the later onset of disease, than other Rb mutations of germinal origin. 相似文献
3.
Determination of the chromosomal site for the human radiosensitive ataxia telangiectasia gene by chromosome transfer 总被引:3,自引:0,他引:3
The chromosomal localization of the gene which complements radiation hypersensitivity of AT cells was studied by microcell-mediated chromosome transfer. A 6-thioguanine-resistant derivative of an immortalized AT cell line, AT2KYSVTG, was used as a recipient for microcell-mediated chromosome transfer from 4 strains of mouse A9 cells, 3 of which carried a human X/11 recombinant chromosome containing various regions of chromosome 11, while the other carried an intact X chromosome. HAT-resistant microcell hybrids were isolated and examined for their radiosensitivity and chromosome constitution. The microcell hybrid clones obtained from the transfer of an intact X chromosome or an X/11 chromosome bearing the pter → q13 region of chromosome 11 did not show a difference in radiosensitivity from parental AT cells, while those obtained from the transfer of X/11 chromosomes bearing either the p11 → qter or the pter → q23 region of chromosome 11 exhibited a marked radioresistance which was comparable to normal human fibroblasts. A HAT-resistant but radiosensitive variant was further obtained from the microcell fusion with an A9 cell strain carrying an X/11 chromosome bearing the 11p11 → qter region, in which a deletion at the 11q23 region was found. The results indicate that the gene which complements a radiosensitive phenotype of AT is located at the q23 region of chromosome 11. 相似文献
4.
Y Namba K Yoshizawa A Ejima T Hayashi T Kaneda 《The Journal of biological chemistry》1969,244(16):4437-4447
5.
Kenji Abe Noboru Kagei Yoshiyuki Teramura Hiroyasu Ejima 《Journal of medical primatology》1993,22(4):237-239
Hepatocellular carcinoma associated with chronic Schistosoma mansoni infection in a chimpanzee, estimated to be a 12-year-old and born in West Africa, is reported. The hepatic tumor appeared as a solitary firm nodule, and histological examination revealed well-differentiated hepatocellular carcinoma with a trabecular pattern. Hepatitis B virus and hepatitis C virus infections were excluded by serological testing in that animal. This is the first report of hepatocellular carcinoma in the chimpanzee with schistosomiasis. 相似文献
6.
Seibu Mochizuki Shingo Seki Masa-aki Ejima Tatsuyuki Onodera Masayuki Taniguchi Shin-ichiro Ishikawa 《Molecular and cellular biochemistry》1993,119(1-2):151-157
The roles of the Na+/H+ exchange system in the development and cessation of reperfusion induced ventricular arrhythmias were studied in the isolated perfused rat heart. The hearts were perfused in the working heart mode with modified Krebs Henseleit bicarbonate (KHB) buffer and whole heart ischemia was induced by a one-way ball valve with 330 beat/min pacing. Ischemia was continued for 15 min followed by 20 min of aerobic reperfusion (control). Amiloride (1.0mM), an inhibitor of the Na+/H+ exchange system, was added to the KHB buffer only during reperfusion (group B) or only during ischemic periods (group C). Electrocardiographic and hemodynamic parameters were monitored throughout the perfusion. Coronary effluent was collected through pulmonary artery cannulation and PO2, PCO2, HCO
3
–
and pH were measured by blood-gas analyzer.The incidence of reperfusion induced ventricular arrhythmias was 100%, 100% and 0% in control, group B and group C, respectively. The mean onset time of termination of reperfusion arrhythmias was significantly shorter in group B than in control. PCO2 increased from 39.0±0.9 to 89.3±6.0 mmHg at the end of ischemia in control and from 40.6±0.4 to 60.5±5.8 in group C, the difference between groups was statistically significant. HCO
3
–
level decreased from 21.8±0.1 to 18.3±0.5 mmol/l in control, however, this decrease was significantly inhibited in group C (from 22.0±0.5 to 20.3±0.2). The increase in PCO2 and the decrease in HCO
3
–
in group B were similar over time to those observed in control. The decrease in pH produced by ischemia was marked in control (from 7.35±0.01 to 6.92±0.04) and group B (from 7.34±0.01 to 6.94±0.02), whereas a decrease in pH was significantly prevented in group C (from 7.34±0.01 to 7.15±0.04). There were no significant differences in PCO2, HCO
3
–
or pH among the three groups during reperfusion.These experiments provide evidence that amiloride significantly prevented the incidence of reperfusion arrhythmias when added only during ischemia and significantly terminated reperfusion arrhythmias when added only during reperfusion. Amiloride may prevent a decrease in pH, due to alterations in PCO2 and/or HCO
3
–
. These changes in PCO2 and HCO
3
–
might be indirectly influenced by inhibition of the Na+/H+ exchange system via Cl–/HCO
3
–
exchange. The mechanism by which amiloride terminates reperfusion arrhythmias seems to involve electrophysiological effects which were not directly addressed in this experiment. 相似文献
7.
Masa-aki Ohto Koji Hayashi Minoru Isobe Kenzo Nakamura 《The Plant journal : for cell and molecular biology》1995,7(2):297-307
Genes coding for sporamin and β-amylase of sweet potato are inducible not only by high levels of metabolizable sugars, such as sucrose, but also by a low concentration of polygalacturonic acid (PGA). Calmodulin inhibitors and EGTA inhibited both the PGA-inducible and the sucrose-inducible accumulation of mRNAs for sporamin and β-amylase in sweet potato. Calmodulin inhibitors, EGTA and La3+, also inhibited the sucrose-inducible expression, in leaves of transgenic tobacco, of a fusion gene, β-Amy:GUS, which consists of the promoter of the β-amylase gene and the coding sequence for β-glucuronidase. The sucrose-inducible expression of the β-Amy:GUS fusion gene was also inhibited by two inhibitors of Ca2+ channels, diltiazem and nicardipine. These results suggest that the sugar-inducible expression of genes for sporamin and β-amylase involves, at least in part, Ca2+-mediated signalling, and that the cytosolic free Ca2+ may mediate cross-talk between signals related to carbohydrate metabolism and other stimuli. Treatment of coelenterazine-loaded leaf discs of tobacco expressing a Ca2+-binding photoprotein, aequorin, with 0.2 M sucrose for 24 h significantly reduced the level of luminescence that could be induced by cold shock, as compared to cold shock-induced luminescence in coelenterazine-loaded leaf discs treated with water. Repression of cold shock-induced luminescence was due to the conversion of holoaequorin to apoaequorin during the treatment with sucrose. Treatment of coelenterazine-loaded leaf discs with a 0.2 M solution of glucose or fructose, but not of mannitol or sorbitol, also reduced the cold shock-induced luminescence. It is suggested that non-synchronous increases in cytosolic level of free Ca2+ occur in leaf discs during treatment with high levels of metabolizable sugars. 相似文献
8.
9.
Target analysis of the PS II reaction in spinach thylakoidsshowed that the respective molecular masses of the catalyticunits for oxygen evolution and the reaction center are about120 kDa and 250 kDa based on a kinetic separation of the tworeaction rates. The size of the oxygen-evolving enzyme agreedwith that determined for the PS II preparation from a thermophiliccyanobacterium by the same means [Nugent and Atkinson (1984)FEBS Lett. 170: 89]. Single hit-inactivation of oxygen evolutionand the PS II reaction center units indicates that each functionis driven by a structurally assembled unit. (Received August 6, 1984; Accepted December 17, 1984) 相似文献
10.