A case of an appendiceal cystadenoma resulting in a large mucocele in a 35 year old man presenting with abdominal pain is reported. On ultrasonography, an unusual appearance of strand-like layers of ...varying echo-texture suggesting a solid lesion was seen. On computed tomography, calcification and contrast enhancement of the rim was noted. The spectrum of imaging appearances of appendix mucoceles is reviewed.
This chapter provides an introduction to current concepts in interorgan nutrition as they relate to protein and amino acid metabolism in the whole body. Methodological issues and their limitations ...are discussed together with assessments of the scope and importance of amino acid flows between tissues and organs. The chapter describes specific interorgan amino acid flows together with the influence of a variety of physiological and pathophysiological conditions upon them. It also highlights the vital role of biomembrane transport of amino acids in the facilitation and control of flows between compartments. It later illustrates the use of metabolic control theory to determine the quantitative importance of transport processes to regulation of amino acid metabolism. The past 5 years have seen very rapid advances in our knowledge of the molecular structure of amino acid transporters. Furthermore, cDNA-encoding transport proteins in important amino acid transport systems, such as A and N, remain to be cloned. Nevertheless, there are already significant challenges and opportunities for the integration of the new molecular knowledge into a holistic view of interorgan amino acid nutrition. Many of the phenomenological descriptions of interorgan nutrition contained in this chapter are capable of being explained on a mechanistic basis by combining the knowledge gained from classical flux measurements with the new molecular information.
即時性功能磁振造影需要線上的影像重組、運動位移修正的影像重新排列及統計功能分析，線上處理系統可提供研究者即時的回饋及功能性磁振造影的品管控制；藉助AFNI（Analysis of Functional NeuroImage, Medical College of Wiscosin, WI, ...USA）影像軟體，研發自裝式線上功能磁振造影分析系統，藉手部運動工作，於六位正常自願受試者及一位硬腦膜瘤病患測試其檢查中的運動位移及功能分析。
於一般功能性磁振造影檢查下，使用Octane工作站可於40秒內獲得線上處理結果，此線上功能磁振造影分析系統可提供臨床功能性磁振檢查的應用及檢查設計的線上回饋，同時該系統無需額外經費並可應用於標準的臨床磁振造影系統。
This chapter focuses on the transport ATPases in detail. Many of the known details of the structure and function of P- and F-type ATPases have been described. While the models developed for the ...thermodynamic coupling between ATP synthesis (or hydrolysis) and ion transport have conjectural components, they are in general founded on a large amount of experimental data and on the resultant ingenious hypotheses of several investigators. One needs to critically assess these impressive findings and insights in order to understand both what we do and what we do not know about how P- and F-type ATPases catalyze transport. While these general similarities in the structure and function of P- and F-type ATPases have undoubted importance, the differences in the details of their proposed structures and mechanisms of action are striking.
If transport proteins migrated across membranes as carriers, solutes could conceivably drive them to one face of membranes with their total chemical potential gradients. In the case of, say, an ...antiporter, the protein could then follow its gradient back to the other face of the membrane carrying a different solute against its gradient. Transport proteins do not, however, migrate across membranes to catalyze transport. Rather, they undergo conformational changes while embedded in them. In the case of transport ATPases, such conformational changes are believed to be a part of the route of transfer of the free energy in phosphoric acid anhydride bonds to that of solute gradients. In contrast to some assessments, it is found in this chapter that the kinetics of antiport and symport may be at least as complex as the kinetics of primary active transport by P- and F-/V-type ATPases. Neither a ping-pong nor a two-site simultaneous model accounts well for the antiport catalyzed by anion exchange (AE) proteins. Moreover, this antiport may exhibit apparently hyperbolic kinetics as well as positive and negative cooperativity depending upon the conditions under which transport is measured. The function of AE proteins is further complicated in vivo owing to their also serving in some cases as channels for regulation of cellular volume. These transport functions may be regulated through interdependent associations of the proteins with other membrane proteins, the cytoskeleton, and cytosolic enzymes involved in intermediary metabolism.
This chapter describes novel aspects of the structures and functions of two distantly related families of K+ channels and emphasizes on similarities in the function of channels and other transport ...proteins. These examples are chosen to represent transport and its regulation via channels that are selective for their substrates. Other channels, such as the a-hemolysin toxin family, differ from the K+ channels discussed in the chapter in the sense that they are not selective and they evolved to lyse cells rather than to contribute to cellular function. Such toxins appear to function like nonselective pores, whereas substrate-selective channels appear to interact intimately with their substrates in a manner that is analogous to enzyme-substrate interactions. While different mechanisms have heretofore been proposed to account for the apparent migration together of more than one substrate ion or molecule via transporters and channels, the chapter encourages the investigators to search for a common explanation for the phenomenon. From such studies, common mechanisms for substrate-selective transport may also begin to emerge.
Much is being learned about how plasma membrane composition and structure are regulated. The anatomy of vesicular trafficking has been described reasonably well, and the biochemical processes that ...achieve proper targeting of lipids and proteins are beginning to be elucidated. Information within the structures of proteins is being discovered that helps to target them to, or retain them in the endoplasmic reticulum, various portions of the Golgi, lysosomes, endosomes, or the plasma membrane. Moreover, investigators in this field are beginning to study how the cell deciphers this information. The mechanisms by which the cytoskeleton and its associated motor proteins help to move vesicles to the correct destinations are also being described, as are the coat, docking, and fusion proteins that result in formation, recognition, and fusion of vesicles with the correct target compartments. One of the most challenging problems in the field appears to be to describe the processes by which lipids and proteins are sorted to apical membranes of polarized cells, since sorting to this compartment appears to differ mechanistically from much of what is known about sorting and vesicular trafficking. In contrast to the emerging nature of knowledge concerning modulation of the function of membrane proteins by membrane lipids and the cytoskeleton, much is already known about the biochemical actions of the proteins. The action of biomembrane transport proteins depends on the formation of a barrier to the free mixing of intracellular and extracellular constituents by the membrane lipid bilayer. Moreover, transport across the membrane barrier frequently results in or requires work.
The study of biomembrane transport requires the consideration of its biophysics and physical chemistry, as well as its biology. Moreover, biomembrane transport is central to the functioning of all ...multicellular organisms regardless of whether it is considered at the subcellular, tissue, or systemic levels of their organization. Similarly, the study of biomembrane transport is as legitimate a component of investigations into mechanisms of development and differentiation as it is into the functioning of fully formed tissues and organs. Hence, there is scarcely a biological journal or a subsection within such journals from the biophysical to the evolutionary levels of investigation that does not contain articles on the subject of biomembrane transport. By analogy, numerous proteins have evolved over billions of years to catalyze transport of solutes and the solvent across the barriers formed by biomembranes. As the demand for different types of transport increased owing to evolution of numerous as well as more complex species, the needed transport processes also evolved. Similarly, as investigations have led to a fuller understanding of biology, the disciplinary boundaries that once helped to define ourselves now help more easily to recognize the various aspects of biology to which unfolding work may apply. Moreover, the contributions of these biomembrane transport processes to the physiological functioning of cells and organisms is rooted in the physical and chemical nature of biomembrane barriers and how the barriers may change in various physiological and pathophysiological conditions.
