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1.
The relationship between spatial and temporal tracer profilesis established, and used to re-analyse reported profiles ofboth types. Evidence of dispersive flow (i.e. a range of transportspeeds) in phloem translocation is obtained from both spatialand temporal profiles. Previous suggestions of plug flow areshown probably to be a consequence of too long a time intervalbetween successive measurements in obtaining these profiles.  相似文献   

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The article reports a comparative study on university students’ linguistic consciousness and world-view. An attempt is made to integrate psycholinguistics with the study of intelligence. Psycholinguistic tools are combined to diagnose indicators of intelligence. A special focus is on linguistic tools for reflection, generalization, and transformation of reality.  相似文献   

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The chylomicron remnant particle is thought to be particularly atherogenic and we have previously shown alterations in post-prandial lipoproteins which could contribute to their atherogenicity. Cholesterol metabolism is disturbed in diabetes, yet the effect of diabetes on intestinal cholesterol synthesis and absorption has rarely been investigated. The aim of this study was to examine cholesterol absorption and intestinal synthesis of cholesterol in the streptozotocin diabetic rat. Twelve diabetic rats were paired with 12 control rats. [14C]-Cholesterol emulsion was administered and the lymph duct was canulated. Lymph was collected for 4 h. At sacrifice blood was taken for plasma lipoprotein measurements. Chylomicrons were prepared from the lymph by ultracentrifugation and [14C]-cholesterol content was determined by liquid scintillation counting. Lymph apolipoprotein B48 was isolated by gradient gel electrophoresis, and quantified by densitometric scanning. Serum triglyceride and cholesterol were greatly elevated in diabetic compared to control animals (260 ± 90 and 9.8 ± 8.0 mg/ml vs. 1.0 ± 0.4 and 0.6 ± 0.3 mg/ml, p < 0.0001 respectively). Lymph chylomicron apo B48 was similar in the two groups. Cholesterol absorption was not significantly different in diabetic compared to control rats but cholesterol synthesis was significantly, higher in the diabetic animals (550 ± 352 vs. 322 ± 113 μg/h p < 0.03). There was a positive correlation between apo B48 and cholesterol absorption (r = 0.70, p < 0.01) in the diabetic rats and control rats (r = 0.71, p < 0.01) but no correlation between apo B48 and cholesterol synthesis in either group. This study demonstrates that cholesterol synthesis was increased in diabetes whereas cholesterol absorption was unaffected suggesting that intestinal cholesterol synthesis made an important contribution to the hypercholesterolaemia seen in the diabetic animals.  相似文献   

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Theories for the dose response analysis of drug combinations have been developed along two separate lines. In the first line, mainly followed by pharmacologists, the concept of “additivity” is of central importance. A corresponding central concept in the second line, which was mainly followed by biometricians, is that of “simple similarity”. We show that simple similarity implies additivity and we give a condition under which the reverse holds.  相似文献   

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姜志龙  杜传书 《遗传学报》1992,19(3):198-202
本文应用等电聚焦电泳技术,调查了广州地区128例白血病、80例原发性肝癌、52例系统性红斑狼疮和1456例正常人的Tf遗传多态性分布。与正常人组相比,急性粒细胞白血病组的Tf~(C_1)基因频率显著增高(P<0.05);TfC_1C_1表型频率也显著高于正常人组(P<0.05),TfC_1C_1人群的患病相对危险率为1.9。未发现急性淋巴细胞白血病、慢性粒细胞白血病、原发性肝癌疾病组的Tf表型和基因频率与正常人组有显著性统计学差异。此外,还发现系统性红斑狼疮组的Tf~(C_2)基因频率显著高于正常人(P<0.025),Tf~(C_1)频率则相应下降(P<0.05);表型频率TfC_1C_2显著增高(P<0.005),相对危险率为2.3,TfC_1C_2相应下降(P<0.01)。  相似文献   

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SYNOPSIS. A diet that has high levels of polyunsaturated fattyacids enhances mammalian torpor. Polyunsaturated fatty acidsare not synthesized by mammals, but are incorporated into bothmembrane and storage lipids when they occur in the diet. Polyunsaturatedfatty acids also undergo autoxidation more readily than otherfatty acids, thereby producing highly toxic lipid peroxides.Lipid peroxidation increases during torpor. Natural selectionin mammalian hibernators should thus have favored the evolutionof dietary preferences that maximize hibernation ability whilesimultaneously minimizing the degree of lipid peroxidation duringtorpor. This hypothesis was tested in laboratory experimentsand field studies involving golden-mantled ground squirrels(Spermophilus lateralis). We found that the intake of polyunsaturatedfatty acids isrestricted during the fall and autoxidation intissues occurs mostly during the later phases of hibernation.  相似文献   

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A major theoretical problem for Soviety psychophysiologists, many of whom base their work on Pavlovian research and theory, is the integration of Pavlovian doctrine into contemporary knowledge from neurophysiology and the burgeoning theoretical work on cybernetics. Neither modern electrophysiological techniques nor cybernetic ideas were available to Pavlov.  相似文献   

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为了研究染色体畸变与微核形成的关系,本实验用不同浓度的丝裂霉素C(MMC,0.025—0.4μg/ml),处理人外周血淋巴细胞,观察中期染色体畸变与不同细胞周期形成的微核间的关系。获得如下主要结果:(1)MMC诱发的染色体畸变细胞率(ACF),未经培养的G_0期淋巴细胞的微核细胞率(NC-MNCF)以及培养的淋巴细胞的微核细胞率(C-MNCF),在一定剂量范围内均呈剂量依赖性增加,并可用幂回归方程描述;(2)微核形成与染色体畸变全然无关的NC-MNCF,和C-MNCF一样,与ACF呈良好的正相关;(3)用胞质分裂阻滞(CB)法,检测MMC诱发的CB-MNCF,较C-MNCF无显著提高,MNCF/ACF的比值较小,并随着MMC剂量增加从0.15左右降到0.03。所有上述结果表明,不能简单理解微核形成与染色体畸变间的关系,在分裂的细胞群体中,中期染色体畸变可能仅是微核形成的一种来源。  相似文献   

10.
为了分析氧化应激诱导的自噬与隐睾症及畸形精子症的相关性,首先采用高通量的qPCR array技术检测44个自噬相关基因在隐睾症患者和生育力正常男性的睾丸组织中的表达差异,筛选出11个表达差异显著的自噬相关基因;然后用不同浓度过氧化氢(hydrogen peroxide, H_2O_2)分别处理小鼠精原细胞系GC-1 spg和睾丸支持细胞系TM4,通过3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐[(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT)]分析H_2O_2处理对细胞增殖活性的影响,并采用实时荧光定量PCR (real-time quantitative PCR, qRT-PCR)检测11个差异表达的自噬相关基因在细胞氧化应激条件下的表达;最后利用GEO (Gene Expression Omnibus)数据库分析自噬相关基因与畸形精子症的关系。通过综合比较发现, BCL2L1、EIF2AK3在隐睾症、畸形精子症及氧化应激过程中均表达上调,表明这两个基因与男性不育的发生有关,推测其作用机制可能是通过响应氧化应激信号来实现。  相似文献   

11.
This review describes the development of the molecular level Ca2+-voltage hypothesis. Theoretical considerations and feedback between theory and experiments played a key role in its development. The theory, backed by experiments, states that at fast synapses, membrane potential by means of presynaptic inhibitory autoreceptors controls initiation and termination of neurotransmitter release. A molecular kinetic scheme which depicts initiation and termination of evoked release is discussed. This scheme is able to account for both spontaneous release and evoked release. The physiological implications of this scheme are enumerated.  相似文献   

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凋亡和自噬是参与维持机体正常的生理平衡和内环境稳定重要机制,与正常生长发育以及肿瘤等多种疾病发展过程都有着密切的联系。对于肿瘤的治疗,传统的方法是诱导肿瘤细胞凋亡,然而,肿瘤细胞中凋亡抗性的出现成为肿瘤治疗的主要障碍。近来,通过诱导其它细胞死亡方式致肿瘤细胞死亡已经成为有潜力的新的抗肿瘤机制。自噬作为另外一种细胞程序性死亡方式与凋亡一样有着复杂的分子机制和调控机制,它们之间存在密切的联系,并且存在许多相同的调节蛋白。本文就凋亡和自噬在形态特征、分子机制、检测方法以及在肿瘤治疗过程两者之间的关系做一综述。  相似文献   

16.
Breakfast skipping is associated with obesity and an increased risk of type 2 diabetes. Later chronotypes, individuals who have a preference for later bed and wake times, often skip breakfast. The aim of the study was to explore the relationships among breakfast skipping, chronotype, and glycemic control in type 2 diabetes patients. We collected sleep timing and 24-h dietary recall from 194 non-shift-working type 2 diabetes patients who were being followed in outpatient clinics. Mid-sleep time on free days (MSF) was used as an indicator of chronotype. Hemoglobin A1C (HbA1C) values were obtained from medical records. Hierarchical linear regression analyses controlling for demographic, sleep, and dietary variables were computed to determine whether breakfast skipping was associated with HbA1C. Additional regression analyses were performed to test if this association was mediated by chronotype. There were 22 participants (11.3%) who self-reported missing breakfast. Breakfast skippers had significantly higher HbA1C levels, higher body mass indices (BMI), and later MSF than breakfast eaters. Breakfast skipping was significantly associated with higher HbA1C values (B?=?0.108, p?=?0.01), even after adjusting for age, sex, race, BMI, number of diabetes complications, insulin use, depressive symptoms, perceived sleep debt, and percentage of daily caloric intake at dinner. The relationship between breakfast skipping and HbA1C was partially mediated by chronotype. In summary, breakfast skipping is associated with a later chronotype. Later chronotype and breakfast skipping both contribute to poorer glycemic control, as indicated by higher HbA1C levels. Future studies are needed to confirm these findings and determine whether behavioral interventions targeting breakfast eating or sleep timing may improve glycemic control in patients with type 2 diabetes.  相似文献   

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This paper is the first of a series of articles dealing with the history and theory of the Zagorsk experiment. A number of philosophers and psychologists have realized the importance of rearing and educating deaf-blind children in the Soviet Union as they believe it reveals the secret of the origin of the human personality. This paper also examines the Zagorsk experiment’s “canonical version,” the Marxist philosophical and psychological interpretations of educating deaf-blind children, and raises the question of whether the facts fit these interpretations. It contends that the Zagorsk experiment expressed the spirit and metaphysics of the Soviet epoch.  相似文献   

18.
A model is developed for predicting the interval-strength relationship in mammalian atrium. The postulates underlying the model relate the intracellular and transmembrane calcium fluxes to changes in contractility. The predictions of the model agree qualitatively with the behavior of atrium for the following patterns of stimulation: (a) constant interval between stimuli, (b) a rest, or period with no stimuli, after the attainment of a steady-state force level, (c) a sudden change in the interval between stimuli, and (d) paired pulse stimulation. The effects of varying several parameters of the model on both the contraction staircases, after a rested-state contraction, and the steady-state interval-strength relationship are examined. Additional considerations are made: (a) estimates are made of the tissue calcium content available for contraction; (b) the physical meaning of the rested-state contraction is discussed; and (c) estimates are made of the proportionality constant between the maximum value of the contractile tension and the amount of calcium released before a contraction.  相似文献   

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Iron absorption by barley, pea, and runner bean is stimulatedby bicarbonate but inhibited by increasing pH. Bicarbonate stimulatestranslocation of Fe in barley but inhibits it in pea and bean.Increasing pH stimulates translocation in barley and pea withno effect in bean. The presence of other ions in the externalsolution appears to inhibit absorption but enhances translocationof Fe in bean and pea. It is concluded that whether or not bicarbonatewill induce chlorosis in a plant depends on species and variety.  相似文献   

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The Relationship Between Adhesion Molecules and Neuronal Plasticity   总被引:3,自引:0,他引:3  
1. It is presently widely assumed that structural reorganization of synaptic architectures subserves the functional gains that define certain neuronal plasticities.2. While target molecules thought to participate in such morphological dynamics are not well defined, growing evidence suggests a pivotal role for cell adhesion molecules.3. Herein, brief discussions are presented on (i) the history of how adhesion molecules became implicated in plasticity and memory processes, (ii) the general biology of some of the major classes of such molecules, and (iii) the future of the adhesion molecule/plasticity relationship.  相似文献   

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