Thin Ascending

Thin ascending limb Fluid entering is hypertonic. The limb is impermeable to water but ion transport does occur, which causes the urine osmolarity to fall. 

PCT is proximal convoluted tubule, DL is descending limb of the loop of Henle, Thin AL is thin ascending limb of the loop of Henle, Thick AL is thick ascending limb of the loop of Henle, DCT is distal convoluted tubule and CD is collecting duct. (This figure is reproduced with permission from Fundamental Principles and Practice of Anaesthesia, P. Hutton, G. Cooper, F. James and J. Butterworth. Martin-Dunitz 2002 pp. 487, illustration no. 25.16.)... 

At the boundary between the inner and outer stripes of the outer medulla, the proximal tubule empties into the thin descending limb of Henle s loop. Water is extracted from the descending limb of this loop by osmotic forces found in the hypertonic medullary interstitium. As in the proximal tubule, impermeant luminal solutes such as mannitol oppose this water extraction. The thin ascending limb is relatively water-impermeable. 

Geraniol [106-24-1] M 154.3, b 230 , d 0.879, n 1.4766. Purified by ascending chromatography or by thin layer chromatography on plates of kieselguhr G with acetone/water/liquid paraffin (130 70 1) as solvent system. Hexane/ethyl acetate (1 4) is also suitable. Also purified by GLC on a silicone-treated column of Carbowax 20M (10%) on Chromosorb W (60-80 mesh). [Porter Pure Appl Chem 20 499 7969.] Stored in full, tightly sealed containers in the cool, protected from light. 

Development of the thin-layer chromatogram is accomplished by placing a small amount of eluent in the bottom of a suitable container, placing the spotted thin layer in the container, sealing it, and allowing the eluent to ascend the layer through capillary action. 

Thin layer chromatography of the solvent extracts was carried out on Whatman LKSDF silica gel 250pm plates. The plates were developed in ascending fashion with 1 1 1 hexane acetone toluene or hexane. After drying, the lanes were divided into 1cm sections and the silica gel recovered for counting of the labelled benzo[a]pyrene and anthracene. 

The most common method of configuring a paper or thin-layer experiment is the ascending configuration shown in Figure 11.12. The mixture to be separated is first spotted (applied as a small spot)... 

Planar Thin layer Ascending, descending, radial Adsorption, partition, ion exchange, size exclusion... 

A round-bottomed flask (capacity 1 1.) is provided with a wellfitting thin-walled double neck attachment (Eig. 30). An ascending Liebig condenser is clamped obliquely and its inner tube is joined by a short wide rubber tube to the oblique neck in such a way that the flask can be vigorously shaken without trouble. The upright neck, which serves for the introduction of the zinc dust required for the reduction, is closed with a cork. 

Both ascending and descending paper chromatographic techniques have been used and, when thin-layer supports are employed, the use of either silica gel or cellulose is applicable. As the number of carbohydrates present in the sample is often small, the careful choice of solvent will generally make it unnecessary to perform the two-dimensional separations that are often needed when large numbers of substances, such as amino acids, are present. Reference solutions of each carbohydrate can be made up in concentrations of approximately 2 g 1 1 dissolved in an isopropanol solvent (10% v/v in water) and samples of about 10 fx should give discernible spots after separation. 

Specimens were post-fixed in 1% OSO4 in sodium cacodylate buffer, dehydrated in ascending alcohol solutions, and embedded in Epon LX 112. Semi-thin sections (1.0 pm thickness) were cut with a diamond knife and stained with Richardson s dye (contains methylene blue) or PAS-reagent. Micrographs were made with an Olympus New Vanox microscope. 

The thick ascending limb (TAL) of the loop of Henle actively reabsorbs NaCI from the lumen (about 25% of the filtered sodium), but unlike the proximal tubule and the thin descending limb of Henle s loop, it is nearly impermeable to water. Salt reabsorption in the TAL therefore dilutes the tubular fluid, and it is called a diluting segment. Medullary portions of the TAL contribute to medullary hypertonicity and thereby also play an important role in concentration of urine by the collecting duct. 

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method,... 

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method, i.e. the solvent creeps up the stationary phase by capillarity. The adsorbent (e.g. silica, alumina, cellulose) is spread on a rectangular glass plate (or solid inert plastic sheet). Some adsorbents (e.g. silica) are mixed with a setting material (e.g. CaSC>4) by the manufacturers which causes the film to set on drying. The adsorbent can... 

Figure 4-20 Separation of a mixture of O-methylated glucoses by ascending thin-layer chromatography. Whatman K6 TLC plates were used with two ascents of the solvent acetonitrile/chloroform/methanol in the ratio 3/9/2, V/...

Chromatography is a separation process which depends on the differential distributions of the components of a mixture between a mobile bulk phase and an essentially thin film stationary phase.53-56 The stationary phase may be either in the form of a packed column (column chromatography) through which a mobile phase is allowed to flow, or in the form of a thin layer adhering to a suitable form of backing material (thin-layer chromatography) over which the mobile phase is allowed to ascend by capillary action. 

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