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The model is based on the assumption that the cell cycle contains a Go-phase which cells leave randomly with a constant probability per unit time, γ. After leaving the Go-phase, the cells enter the C-phase which ends with cell division. The C-phase and its constituent phases, the‘true’G1-phase, the S-phase, the G2-phase and mitosis are assumed to have constant durations of T, T1Ts, T2 and Tm, respectively. For renewal tissue it is assumed that the probability per unit time of being lost from the population is a constant for all cells irrespective of their position in the cycle. The labelled mitosis curve and labelling index for continuous labelling are derived in terms of γ, T, and Ts. The model generates labelled mitosis curves which damp quickly and reach a constant value of twice the initial labelling index, if the mean duration of the Go-phase is sufficiently long. It is shown that the predicted labelled mitosis and continuous labelling curves agree reasonably well with the experimental curves for the hamster cheek pouch if T has a value of about 60 hr. Data are presented for the rat dorsal epidermis which support the assumption that there is a constant probability per unit time of a cell being released from the Go-phase. 相似文献
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在分析菌紫质光驱质子泵过程的基础上 ,应用Hong的化学电容的概念 ,提出在菌紫质人工膜系统中等效存在C -电容和N -电容 ,并由此研究了铁/紫膜/胶/铜光电池在光触发瞬时的界面电势。结果可提供于以菌紫质为基础的分子电子器件 ,和菌紫质光驱质子泵机理的研究。 相似文献
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Abstract— The energy state of brain tissue was evaluated from the tissue concentrations of ATP, ADP and AMP and the cytoplasmic NADH/NAD+ ratio from the tissue, CSF and blood concentrations of lactate and pyruvate, and from the intracellular pH', in rats exposed to carbon dioxide concentrations of 640 per cent. The hypercapnia had no significant effect on the energy state of the tissue. Hypercapnia of increasing severity gave rise to a progressive decrease in the pyruvate concentration; the lactate concentration fell at low CO2 concentrations, but no further decrease was observed at CO2 concentrations greater than 20 per cent. There was a progressive rise in the intracellular lactate/pyruvate ratio at increasing CO2 concentrations, corresponding to the fall in intracellular pH, i.e. the calculated NADH/NAD+ ratios remained normal. It is therefore concluded that hypercapnia does not affect the cytoplasmic redox state. 相似文献
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Abstract Experiments were carried out to study the relationship between the quantity of honeydew and rm of green peach aphid infesting 50 tobacco varieties in the field from 1990 to 1992. The results showed that the range for rm is from 0.102 to 0.498, for honeydew secreted during 24 hours is 3.862 mm2 /aphid to 29. 356 mm2 /aphid. It also showed that the resistance of tobacco varieties to green peach aphid manifested in the reduction of net reproductive rate. Both rm and honeydew had significant relations to the population of green peach aphid in the field, and therefore the quantity of honeydew can be used as an index in determination of tobacco resistance to green peach aphid. 相似文献
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以虾夷扇贝(Mizuhopecten yessoensis)的生长性状、闭壳肌脂肪酸组成与含量、闭壳肌C、N元素含量及其比值为主要考察指标, 在对比选育家系的生长性状差异的基础上, 分析了不同生长速度的虾夷扇贝家系闭壳肌脂肪酸组成与含量差异, 研究了闭壳肌C、N元素含量及其C/N比值与脂肪酸含量的相关性。结果表明, 不同扇贝家系闭壳肌的主要脂肪酸含量差异较小而相对丰度差异明显, EPA (3.59—4.09 mg/g)和DHA (3.03—3.46 mg/g)之和占比扇贝闭壳肌脂肪酸总量的47.19%—49.32%; 不同家系的虾夷扇贝闭壳肌C、N元素稳态性较好, C元素和N元素的含量分别为(39.21±0.04)%和(10.62±0.16)%, C/N比值为3.70±0.06; 相关分析表明家系闭壳肌C/N比值与TFA、SFA、PUFA、EPA以及DHA等脂肪酸含量呈显著负相关。因此, 在进行虾夷扇贝生长相关选择育种时, 可以结合闭壳肌脂肪酸组成与含量、闭壳肌元素C/N比值开展复合性状选育, 从而为扇贝闭壳肌高品质脂肪酸家系选育提供科学依据。 相似文献
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INCORPORATION OF 3 H-LABELLED LEUCINE INTO THE PROTEIN FRACTION IN THE RETINA OF THE HONEYBEE DRONE 总被引:2,自引:0,他引:2
Abstract— Protein synthesis in the retina of the honey-bee drone was studied by incubating head slices in labelled leucine and measuring the TCA insoluble radioactivity. It was found that the protein-bound radioactivity in illuminated retinas was half of that in dark-adapted ones. This ratio was not affected by pre-treatment with puromycin. It was therefore concluded that, in the drone, the main influence of illumination is to increase the rate of breakdown of proteins.
Relatively high concentrations of labelled protein were found in dark-adapted retinas when the retinula cells were hyperpolarized by bathing the preparation in a sodiumfree medium; low concentrations were found when retinula cells were depolarized by increasing the extracellular potassium concentration. These findings suggest that protein metabolism of the retina is influenced by the membrane potential of retinula cells. 相似文献
Relatively high concentrations of labelled protein were found in dark-adapted retinas when the retinula cells were hyperpolarized by bathing the preparation in a sodiumfree medium; low concentrations were found when retinula cells were depolarized by increasing the extracellular potassium concentration. These findings suggest that protein metabolism of the retina is influenced by the membrane potential of retinula cells. 相似文献
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THE DURATION OF THE G1 PHASE OF THE MITOTIC CYCLE AND ITS RELATION TO RADIOSENSITIVITY 总被引:3,自引:3,他引:0
F. A. L. CLOWES 《The New phytologist》1965,64(3):355-355
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21世纪初,古新统/始新统界线(简称P/E界线)被国际地层委员会正式定义为古新世-始新世极热事件(简称PETM)期间碳同位素负漂的开始。然而,P/E界线在特提斯大有孔虫生物带(简称SBZ)中的具体位置却一直争论不休。本文回顾了国内外学者近二十年来对P/E界线的研究成果,认为P/E界线应该位于SBZ5的内部,而非SBZ4和SBZ5的界线处。在P/E界线处,大有孔虫没有发生明显的组分上的变化。而在P/E界线后的5—12万年内,大有孔虫发生了一次绝灭。这个绝灭事件被称为大有孔虫的绝灭和新生(简称LFEO)。大有孔虫的绝灭和新生不同于传统上认为的大有孔虫更替事件(简称LFT)。前者可能是由PETM后期强烈的陆地风化剥蚀引起海水富营养化后所造成的一次灾变事件,而后者代表了大有孔虫在长期稳定的浅海环境中形成的演化上的成功。通过回顾P/E界线的研究历史,笔者认为绝大部分地层剖面在P/E界线处的不连续性/不完整性是产生这些争议的主要原因。 相似文献
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文章采用组织切片、生化组分分析以及实时荧光定量PCR等方法,研究了大鳞副泥鳅(Paramisgurnus dabryanus)、泥鳅(Misgurnus anguillicaudatus)和北方泥鳅(Misgurnus bipartitus)肉质差异。结果显示:大鳞副泥鳅、泥鳅和北方泥鳅的肌纤维横截面积分别为(3589.17±2326.01)、(2809.7±1818.69)和(2511.93±1949.03)μm2。粗蛋白和粗脂肪含量均是大鳞副泥鳅最高[分别为(17.07±0.31)%和(2.57±0.38)%],依次为泥鳅[分别为(14.57±0.59)%和(1.37±0.12)%]和北方泥鳅[分别为(12.33±0.15%和0.57±0.06%]。必需氨基酸指数(EAAI)依次为泥鳅(74.38)、大鳞副泥鳅(65.11)和北方泥鳅(60.14);呈味氨基酸含量依次为泥鳅(32.60±1.64)%、大鳞副泥鳅(27.75±2.13)%和北方泥鳅(24.86±1.00)%;除亚油酸以外的总多不饱和脂肪酸含量依次为北方泥鳅(24.43±0.26)%、泥鳅(24.18±1.99)%和大... 相似文献
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Experiments in mice on the fraction of haemopoietic stem cells in S-phase after irradiation indicated that a large fraction of the cells resting in G0 will enter S-phase after a very short interval of time.
After excluding alternative explanations it must be concluded that cells in G0 have completed all preparations for going into S-phase or, in other words, that the localization of these G0 cells in relation to other phases of the cell cycle must be between G1 and S-phase. 相似文献
After excluding alternative explanations it must be concluded that cells in G
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研究于2015—2017年对珠江流域12个站位的日本鳗鲡(Anguilla japonica)及花鳗鲡(Anguilla mar-morata)种群资源量与洄游路线等进行了初步调查, 并对其资源量状况、空间分布特征与环境影响因素等进行了分析。结果显示在近3年的调查时间里, 共采集到日本鳗鲡41尾, 平均年龄为(4.2±1.3)龄, 93%的个体未性成熟; 采集到花鳗鲡12尾, 平均年龄为(4.3±1.0)龄, 83%的个体未性成熟。日本鳗鲡在珠江水系最远能分布到红水河的合山江段, 其在渔获物中的数量百分比与重量百分比均低于百分之一; 花鳗鲡最远能分布到西江的石龙江段, 其在渔获物中的出现率低于两百分之一。珠江水系鳗鲡野生资源极度匮乏, 保护形势十分严峻。同时发现日本鳗鲡空间分布主要受河流分维和河流宽度的影响; 花鳗鲡的空间分布主要受河流宽度和水深的影响。该研究是珠江水系野生渔业资源长期调查的一部分, 研究结果将对鳗鲡资源的保护和可持续利用具有指导意义。 相似文献
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JENNIFER L. SCHMELDER ROBIN M. KALINOWSKI PETER W. BODNARUK 《Journal of Rapid Methods and Automation in Microbiology》2000,8(1):65-70
Aerobic plate counts (APC) are used by the food industry to help determine the sanitary state of equipment and bacterial load of finished product. Conventional aerobic count methods for processed meats require approximately 72 h incubation before results are available. Food processing plants with in-house analytical laboratories require methods that are simple, reliable and rapid. New test methods using PetrifilmTM (PF) and RedigelTM (RG) have been developed for determining APC. These methods are faster and easier than culturing in a standard agar medium. A variety of raw, cooked; cured and noncured meat products, cooling brine and environmental surface swabs were collected and analyzed for APC using PF, RG and plate count agar (PCA). Data analyses from over 200 samples indicated that the sensitivity of rapid testing methods for aerobic bacteria can vary depending on sample type. 相似文献