Membranes liver cell

Cholesterol is found in many biological membrane and is the main sterol of animal organisms. It is eqnimolar with phospholipids in membranes of liver cell, erythrocytes, and myelin, whereas in human stratum comeum it lies in the outermost layer of the epidermis... 

The inhibition of amino-acid transport has been regarded as the main toxic effect of mercury compounds [82], The biochemical mechanism underlying the inhibition is unclear. In unfertilized sea-urchin eggs an interaction with the amino-acid carrier was found, whereas in fertilized eggs inhibition of amino-acid transport was indirect and might result from an elevation of the Na + content of the egg caused by the inhibition of the Na+ pump [83]. The action on the diffusional process could be mediated by an effect on membrane phospholipids or on membrane proteins, or by interaction with Ca2+ which stabilizes membrane structure. Mercuric chloride in skate liver cells inhibited amino acid transport, decreased Na + /K + -ATPase (adenosinetriphosphatase) activity, impaired volume regulatory mechanisms and increased the permeability of the plasma membrane to potassium [84]. It has been suggested that... 

An anomaly associated with citrulline that became evident when detailed kinetic studies were made in the 1950s (R.B. Fisher and J.R. Bronk) was the irreproducibility of its catalytic activity in liver slices on the formation of urea, despite the clear evidence from Ratner and Petrack of its importance in arginine synthesis. Initially the discrepancy in catalytic activity between ornithine and citrulline was ascribed to the possible impermeability of the liver cell plasma membrane to the latter intermediate, a hypothesis which was rapidly disproved experimentally. Only recently has it been shown that ornithine transcarbamylase is clearly associated with the ornithine/... 

Unconjugated bilirubin is taken into the hepatocytes by binding to membrane transport proteins and transported through the liver cells to the SER by proteins called ligandins. The SER is the location of a specific bilirubin-UDP-glucuronosyl transferase... 

Hepatocellular necrosis related to covalent binding of metabolites to cell and plasma proteins and to mitochondrial membrane damage results in release of intracellular enzymes into the bloodstream, providing biomarkers of liver cell damage. Biomarkers of hepatocellular necrosis are not specific to... 

A patient has been exposed to a toodc compound that increases the permeability of mitochondrial membranes for protons. Which of the following events in liver cells would you expect to occur ... 

Telang S, Tony C, Williams GM. 1982. Epigenetic membrane effects of a possible tumor promoting type on cultured liver cells by the non-genotoxic organochlorine pesticides chlordane and heptachlor. Carcinogenesis 3 1175-1178. 

Like living organisms themselves, cells come in a remarkable variety of flavors. Brown has described what might be a human cell with elaborate internal structure. However, there is no such a thing as a typical cell. Afunctional liver cell, a hepatocyte, is quite distinct from a nerve cell, a neuron, that, in turn, is not much like a cell of the retina of the eye. Skin cells, pancreatic cells, kidney cells, cells of the testis and ovary, red blood cells, bone cells, and on and on, are all structurally, functionally, and metabolically distinct. Indeed, there are several types of cells in the skin, pancreas, kidney, testis, ovary, and bone. Then there are the cells of bacteria and other microorganisms that have no nucleus or other membrane-limited organelles very different. Diversity abounds. 

Hepatocytes make up 60-70% of the total number of liver cells. They have a well-organized intracellular structure with huge numbers of cell organelles to maintain the high metabolic profile. At the apical side or canalicular membrane the cell is specialized for the secretion of bile components. There are several ATP-dependent transport carriers located on this side of the membrane, which transport bile salts, lipids and xenobiotics into the canaliculus. On the sinusoidal side, the cells specialize in uptake and secretion of a wide variety of components. To increase the surface of the membrane for this exchange with the bloodstream, the sinusoidal domain of the membrane is equipped with irregular microvilli. The microvilli are embedded into the fluid and matrix components of the space of Disse and are in close contact with the sinusoidal blood because of the discontinuous and fenestrated SECs. To facilitate its metabolic functions numerous membrane transport mechanisms and receptors are situated in the membrane. 

To make quantitative predictions of DDI for the new compound as perpetrator, a reliable estimate of a relevant in vivo concentration is needed. What is tmly needed is knowledge of the concentration of the inhibitor available to bind to the enzyme. For liver, if the well accepted free-dmg hypothesis (which underwrites fundamental drug action principles in pharmacology) is applied for DDI, then the use of a free intracellular liver concentration is needed. For inhibitors that are permeable through membranes, the free concentration in the portal vein should serve as the closest proxy for free intracellular concentration in the liver. Diminished permeability as well as active uptake and efflux from liver cells can confound this relationship. Nevertheless, use of estimates of unbound portal vein concentrations (which can be estimated from... 

The answer is D. This patient s tests indicate that he has severe hypercholesterolemia and high blood pressure in conjunction with atherosclerosis. The deaths of several of his family members due to heart disease before age 60 suggest a genetic component, ie, familial hypercholesterolemia. This disease results from mutations that reduce production or interfere with functions of the LDL receptor, which is responsible for uptake of LDL-cholesterol by liver cells. The LDL receptor binds and internalizes LDL-choles-terol, delivers it to early endosomes and then recycles back to the plasma membrane to pick up more ligand. Reduced synthesis of apoproteins needed for LDL assembly would tend to decrease LDL levels in the bloodstream, as would impairment of HMG CoA reductase levels, the rate-limiting step of cholesterol biosynthesis. Reduced uptake of bile salts will also decrease cholesterol levels in the blood. 

Keywords. Bioartificial liver, cell culture, hollow fiber bioreactor, flat membrane bioreactor, spheroids... 

Fig. 4. Primary liver cells are cultivated on the exterior surfaces of semipermeable capillary hollow fiber membranes. Medium is perfused through the extrafiber space. Through the fibers oxygen supply is supported...

Bader et al. [35] and De Bartolo et al. [36] developed the flat membrane bioreactor which consists of a multitude of stackable flat membrane modules as shown in Fig. 5. Each module has an oxygenating surface area of 1150 cm. Up to 50 modules can presently be run in parallel mode. Isolated hepatocytes are co-cultured with non-parenchymal cells. Liver cells are located of a distance of 20 pm of extracellular matrix from a supported polytetrafluorethylene (PTFE) film. Medium and cells in the modules are oxygenated in the incubator by molecular diffusion of air across the non-porous PTFE membrane. The design of the bioreactor is also the basis for its proven potential for cryostorage with fully differentiated adult primary human liver cells. 

Reverdin EC, Weingart R Electrical properties of the gap junctional membrane studied in rat liver cell... 

Williams GM, Tong C, Telang S. 1984. Polybrominated biphenyls are nongenotoxic and produce an epigenetic membrane effect in cultured liver cells. Environ Res 34 310-320. 

Bile is an aqueous solution of bile salts, inorganic salts, bile pigments, fats, cholesterol, and others. The physiology of bile secretion is not simple, as it involves the active excretion of organic solutes from the blood to the bile. Bile is collected directly from the liver cells through separate channels, without being mixed with blood. The liver cell membrane incorporates extremely fine passages that permit bile secretion. 

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