Impairment of rapid axonal transport and concomitant anomaly of smooth endoplasmic reticulum in acrylamide induced neuropathy]

The axonal transport of proteins was studied by radioautography in preganglionic axons of ciliary ganglia in Leghorn chickens treated by acrylamide. The slow axonal transport of proteins was hardly affected. In contrast, the fast axonal transport was severely impaired. Indeed, radioactive proteins accumulated focally at the periphery of several preterminal axons in regions showing a local disorganization of the smooth endoplasmic reticulum which seemed to be one of the earliest changes induced by acrylamide.     

Transport of sodium,water, 3-O-methyl-glucose and L-phenylalanine in vitro in biotin-deficient rats intestine

Summary In biotin-deficient rats, a decreased intestinal transport of Na⁺, H₂O and L-phenylalanine, and no transport differences of 3-O-methyl-D-glucose were observed. The lower Na⁺ and L-phenylalanine transport appears to be referable to a decreased energy availability and probably not to the lack of a carrier.     

Effect of bombesin on glucose transport system in biomembranes

Summary Bombesin is able to stimulate the glucose transport system supported by a contractile glucose binding protein (GBP) in biomembranes. The increase of glucose transport indicates that bombesin affects GBP.     

Cellular uptake of long-chain fatty acids: role of membrane-associated fatty-acid-binding/transport proteins

The critical importance of long-chain fatty acids in cellular homeostasis demands an efficient uptake system for these fatty acids and their metabolism in tissues. Increasing evidence suggests that the plasma-membrane-associated and cytoplasmic fatty-acid-binding proteins are involved in cellular fatty acid uptake, transport and metabolism in tissues. These binding proteins may also function in the fine tuning of cellular events by modulating the metabolism of long-chain fatty acids implicated in the regulation of cell growth and various cellular functions. Several membrane-associated fatty-acid-binding/transport proteins such as plasma membrane fatty-acid-binding protein (FABPpm, 43 kDa), fatty acid translocase (FAT, 88 kDa) and fatty acid transporter protein (FATP, 63 kDa) have been identified. In the feto-placental unit, preferential transport of maternal plasma arachidonic and docosahexaenoic acids across the placenta is of critical importance for fetal growth and development. Our studies have shown that arachidonic and docosahexaenoic acids are preferentially taken up by placental trophoblasts for fetal transport. The existence of a fatty-acid-transport system comprising multiple membrane-binding proteins (FAT, FATP and FABPpm) in human placenta may be essential to facilitate the preferential transport of maternal plasma fatty acids in order to meet the requirements of the growing fetus. The preferential uptake of arachidonic and docosahexaenoic acids by the human placenta has the net effect of shunting these maternal plasma fatty acids towards the fetus. The roles of plasma membrane-associated binding/transport proteins (FABPpm, FAT and FATP) in tissue-specific fatty acid uptake and metabolism are discussed.     

Transport of a low molecular weight extracellular esterase into membrane vesicles ofCandida lipolytica

Summary The low mol. wt extracellular esterase ofCandida lipolytica is actively transported into membrane vesicles. In the absence of metabolic energy, a proton gradient can drive the transport process. The transport system does not accumulate the enzyme at peak levels due to the presence of a leak pathway.     

Lytic transglycosylases in macromolecular transport systems of Gram-negative bacteria

The cell wall of Gram-negative bacteria is essential for the integrity of the bacterial cell but also imposes a physical barrier to trans-envelope transport processes in which DNA and/or proteins are taken up or secreted by complex protein assemblies. The presence of genes encoding lytic transglycosylases in macromolecular transport systems (bacteriophage entry, type II secretion and type IV pilus synthesis, type III secretion, type IV secretion) suggests an important role for these specialised cell-wall-degrading enzymes. Such enzymes are capable of locally enlarging gaps in the peptidoglycan meshwork to allow the efficient assembly and anchoring of supramolecular transport complexes in the cell envelope. In this review, current knowledge on the role and distribution of these specialised murein-degrading enzymes in diverse macromolecular transport systems is summarised and discussed.Received 13 February 2003; received after revision 25 April 2003; accepted 12 May 2003     

Amino acid transport by small and large intestine of newborn pig

Summary Unidirectional fluxes of different amino acids have been determined across newborn pig small intestine and colon. The systems responsible for amino acid transport are present in the same proportion in both tissues. Colonic transport of amino acids appears to represent a transient overspill function of the small intestine.     

Thiamine-binding activity of Saccharomyces cerevisiae plasma membrane

The specific binding activity to [14C]thiamine was found to be located in hte plasma membrane of Saccharomyces cerevisiae. The activity was inhibited by several thiamine analogs and it was hardly detectable in the plasma membrane from a thiamine transport mutant of Saccharomyces cerevisiae. Some properties of the thiamine-binding activity of yeast plasma membrane are discussed in connection with those of the thiamine transport system.     

Axonal transport of neurofilaments in normal and disease states

Neurofilaments are among the most abundant organelles in neurones. They are synthesised in cell bodies and then transported into and through axons by a process termed 'slow axonal transport' at a rate that is distinct from that driven by conventional fast motors. Several recent studies have now demonstrated that this slow rate of transport is actually the consequence of conventional fast rates of movement that are interrupted by extended pausing. At any one time, most neurofilaments are thus stationary. Accumulations of neurofilaments are a pathological feature of several human neurodegenerative diseases suggesting that neurofilament transport is disrupted in disease states. Here, we review recent advances in our understanding of neurofilament transport in both normal and disease states. Increasing evidence suggests that phosphorylation of neurofilaments is a mechanism for regulating their transport properties, possibly by promoting their detachment from the motor(s). In some neurodegenerative diseases, signal transduction mechanisms involving neurofilament kinases and phosphatases may be perturbed leading to disruption of transport. Received 11 July 2001; received after revision 30 August 2001; accepted 31 August 2001     

基于PLC的车间运输小车的自动控制系统设计

将PLC应用到车间运输小车电气控制系统中，可实现运输小车的自动化控制，降低系统的运行费用。PLC运输小车电气控制系统具有连线简单，控制速度快，精度高，可靠性和可维护性好，安装、维修和改造方便等优点。PLC的控制是论文研究重点之一。在车间运输需求分析的基础上。通过概念的设计、逻辑结构设计和物理结构设计，建立了一套适应车间运输的控制系统。     

The CorA family: Structure and function revisited

The CorA family is a group of ion transporters that mediate transport of divalent metal ions across biological membranes. Metal ions are essential elements in most cellular processes and hence the concentrations of ions in cells and organelles must be kept at appropriate levels. Impairment of these systems is implied in a number of pathological conditions. CorA proteins are abundant among the prokaryotic organisms but homologues are present in both human and yeast. The activity of CorA proteins has generally been associated with the transport of magnesium ions but the members of the CorA family can also transport other ions such as cobalt and nickel. The structure of the CorA from Thermotoga maritima, which also was the first structure of a divalent cation transporter determined, has opened the possibilities for understanding the mechanisms behind the ion transport and also corrected a number of assumptions that have been made in the past.     

Membrane-traversing mechanism of thyroid hormone transport by monocarboxylate transporter 8

Monocarboxylate transporter 8 (MCT8) mediates thyroid hormone (TH) transport across the plasma membrane in many cell types. In order to better understand its mechanism, we have generated three new MCT8 homology models based on sugar transporters XylE in the intracellular opened (PDB ID: 4aj4) and the extracellular partly occluded (PDB ID: 4gby) conformations as well as FucP (PDB ID: 3o7q) and GLUT3 (PDB ID: 4zwc) in the fully extracellular opened conformation. T₃-docking studies from both sides revealed interactions with His192, His415, Arg445 and Asp498 as previously identified. Selected mutations revealed further transport-sensitive positions mainly at the discontinuous transmembrane helices TMH7 and 10. Lys418 is potentially involved in neutralising the charge of the TH substrate because it can be replaced by charged, but not by uncharged, amino acids. The side chain of Thr503 was hypothesised to stabilise a helix break at TMH10 that undergoes a prominent local shift during the transport cycle. A T503V mutation accordingly affected transport. The aromatic Tyr419, the polar Ser313 and Ser314 as well as the charged Glu422 and Glu423 lining the transport channel have been studied. Based on related sugar transporters, we suggest an alternating access mechanism for MCT8 involving a series of amino acid positions previously and newly identified as critical for transport.     

Variations in alpha-aminoisobutyric acid transport during in vitro differentiation of cultured myocardial cells from newborn rats]

The transport of alpha-aminoisobutyric acid has been studied as a function of age in heart cell cultures derived from new-born Rats. The specific rate of alpha-aminoisobutyric acid transport decreased slightly once confluency had been reached and then, from day 8 on, increased abruptly. This last phase may be related to the expression of specialized functions encountered in older cultures.     

The loss of biological activity of 5-hydroxytryptamine creatinine sulphate

Summary 5-Hydroxytryptamine creatinine sulphate loses its biological activity when maintained at room temperature. The loss of 5-HT activity (in stimulating sodium transport across frog skin) is greater than the loss of creatinine sulphate activity (inhibition of sodium transport).     

运输平衡理论解决城市道路交通规划与组织问题的探索

分析了运输平衡理论的平衡关系，提出用运输平衡理论解决城市道路交通问题的方法，得出了用运输平衡理论进行运输系统规划时应注重发展与变化的两点结论，并进行了实证分析。     

The loss of biological activity of 5-hydroxytryptamine creatinine sulphate.

5-Hydroxytryptamine creatinine sulphate loses its biological activity when maintained at room temperature. The loss of 5-HT activity (in stimulating sodium transport across frog skin) is greater than the loss of creatinine sulphate activity (inhibition of sodium transport).     

生物能量在生命体中传递的新理论及实验证实

我们从蛋白质的分子结构和ATP水解所放出能量的特征出发,提出了一个新的生物能量传递理论。并用新的哈密顿函数和波函数代替了原来旧的函数,用解析的方法求出了传递生物能量的孤子在其生理温度和它的寿命时间内能够传递过上千个氨基酸分子,于是它可能是传递生物能量的真正载流子。用解析和数值模拟的方法研究了这种传递生物能量孤子的特性和在生理温度300K时的热力学稳定性,证明了这种孤子在生理温度时是十分稳定的,它的寿命能达到300ps,可能是生物能量的传递者。再通过实验测定了在胶原蛋白和牛血清蛋白等(-螺旋蛋白的光谱特性及其在27-95℃范围内其谱线分布和谱线强度随温度的变化,把所检测的三个结果与能量传递的理论预示的结果相比较,发现它们完全一致,从而从实验上证明了在蛋白质分子中建立的生物能量传递理论是正确的。而理论预示的孤子是蛋白质当中生物能量传递的真正载流子。     

Inhibition of thiamine transport in baker's yeast by methylene blue

Summary Methylene blue was found to inhibit thiamine transport competitively (K_i=0.63 M) in baker's yeast. The dye was also effective in abolishing the growth inhibition ofSaccharomyces cerevisiae by pyrithiamine which is known to be taken up by a common transport system for thiamine in yeast cells. A possible mechanism for the inhibition by methylene blue of the thiamine transport system in baker's yeast is discussed.     

Kinesins in the nervous system

Both the development and the maintenance of neurons require a great deal of active cytoplasmic transport. Much of this transport is driven by microtubule motor proteins. Membranous organelles and other macromolecular assemblies bind motor proteins that then use cycles of adenosine 5'-triphosphate hydrolysis to move these 'cargoes' along microtubules. Different sets of cargoes are transported to distinct locations in the cell. The resulting differential distribution of materials almost certainly plays an important part in generating polarized neuronal morphologies and in maintaining their vectorial signalling activities. A number of different microtubule motor proteins function in neurons; presumably they are specialized for accomplishing different transport tasks. Questions about specific motor functions and the functional relationships between different motors present a great challenge. The answers will provide a much deeper understanding of fundamental transport mechanisms, as well as how these mechanisms are used to generate and sustain cellular asymmetries.     

Structure and function of eukaryotic peptide transporters

The cotransport of protons and peptides is now recognised as a major route by which dietary nitrogen is absorbed from the intestine, and filtered protein reabsorbed in the kidney. Recently, molecular biology has had a very substantial impact on the study of peptide transport, and here we review the molecular and functional information available within the framework of physiology. To this end we consider not only the mammalian peptide transporters and their tissue distribution and regulation but also those from other species (including Caenorhabditis elegans) which make up the proton-dependent oligopeptide transport superfamily. In addition, understanding the binding requirements for transported substrates may allow future design and targeted tissue delivery of peptide and peptidomimetic drugs. Finally, we aim to highlight some of the less well understood areas of peptide transport, in the hope that it will stimulate further research into this challenging yet exciting topic.