scholarly journals On the nature and permeability of chitin II—The permeability of the uncalcified chitin lining the foregut of homarus

1936 ◽  
Vol 120 (816) ◽  
pp. 15-41 ◽  
Keyword(s):  
Thin Layer ◽  
Osmotic Pressure ◽  
Chemical Nature ◽  
Biological Significance ◽  
Decapod Crustacea ◽  
End Products ◽  
Vital Stains ◽  
Physical Tests ◽  
Pass Through ◽  
Broad Outline

It has been shown (Yonge, 1932) that the integument of the Decapod Crustacea, as exemplified by the uncalcified lining of the foregut of the lobster, Homarus vulgaris , consists of two layers which differ widely in nature and origin. There is a thin superficial cuticle which is hyaline, possesses adsorbed lipin, and is formed by the widely distributed tegumental glands the function of which had previously been obscure. The actual chemical nature of this thin layer was not determined but it is not chitin from which it can be distinguished by a variety of chemical and physical tests. The underlying and much thicker layer of the integument consists of lamellated chitin formed by the cells of the epithelium. The present research was designed to determine in broad outline the permeability of this membranous integument, and in particular the influence upon this of the bounding cuticle and the general biological significance of the cuticle. In the Crustacea, Jordan and Lam (1918) found that the foregut and hindgut of Astacus , which are lined with chitin, behave as semipeimeable membranes, allowing water, but not dissolved substances, either electrolytes or non-electrolytes, to pass through under the influence of osmotic pressure. Similar results were obtained by Yonge (1924) with the foregut of Nephrops . Very different results were obtained from similar experiments with the midgut of both Astacus and Nephrops , indicating that the peculiar properties of the remainder of the gut are due to the chitinous lining. Murlin (1902) and Nicholls (1931) have shown that the chitin which lines the so-called midgut in Oniscus, Porcellio , and other land Isopoda, and in Ligia oceanica respectively, is permeable to the end-products of digestion. Krogh (1915) states that the gills of Astacus are practically impermeable to urethane. Fischel (1908), Koehring (1930, 1931), Gickelhorn (1931), and Bond (1933) have all found some evidence for the penetration of the integument of various Cladocera and Copepoda by vital stains.

THE LESS-POLAR METABOLITES PRODUCED BY INCUBATION OF TESTOSTERONE-4-14C WITH RAT AND BOVINE BRAIN

1969 ◽  
Vol 61 (4) ◽  
pp. 641-648 ◽  
Author(s):  
Leon J. Sholiton ◽  
Emile E. Werk
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Paper Chromatography ◽  
Specific Activity ◽  
Bovine Brain ◽  
Polar Fraction ◽  
End Products ◽  
Polar Metabolites ◽  
Layer Chromatography ◽  
Constant Specific Activity

ABSTRACT Rat and bovine brain have been incubated with testosterone-4-14C under standard conditions. With use of paper chromatography, the extracted metabolites were noted to fall into less-polar, iso-polar, and more polar fractions. The components of the less-polar fraction were separated by acetylation and thin-layer chromatography and the major end-products identified by recrystallization to constant specific activity or constant 3H/14C ratios. Androst-4-enedione and 5α-dihydrotestosterone were formed consistently under the conditions utilized. Trace amounts of other less-polar metabolites were noted occasionally.

scholarly journals THE ACCUMULATION OF ELECTROLYTES

1932 ◽  
Vol 15 (6) ◽  
pp. 667-689 ◽  
Author(s):  
W. J. V. Osterhout ◽  
W. M. Stanley
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Aqueous Phase ◽  
Thermodynamic Potential ◽  
Ph Value ◽  
Molecular Form ◽  
External Solution ◽  
Aqueous Layer ◽  
The Difference ◽  
Pass Through

Inasmuch as attempts to explain accumulation by the Donnan principle have failed in the case of Valonia, a hypothesis of the steady state has been formulated to explain what occurs. In order to see whether this hypothesis is in harmony with physico-chemical laws attempts have been made to imitate its chief features by means of a model. The model consists of a non-aqueous layer (representing the protoplasmic surface) placed between an alkaline aqueous phase (representing the external solution) and a more acid aqueous phase (representing the cell sap). The model reproduces most of the features of the hypothesis. Attention may be called to the following points. 1. The semipermeable surface is a continuous non-aqueous phase. 2. Potassium penetrates by combining with an acid HX in the non-aqueous layer to form KX which in turn reacts with an acid HA in the sap to form KA. Since KX is little dissociated in the non-aqueous layer potassium appears to pass through it chiefly in molecular form. 3. The internal composition depends on permeability, e.g., sodium penetrates less rapidly than potassium and in consequence potassium predominates over sodium in the "artificial sap." The order of penetration in the model is the same as in Valonia, i.e., K > Na > Ca > Mg, and Cl > SO4, but the quantitative resemblance is not close, e.g., the difference between potassium and sodium, and chloride and sulfate is much less in the model. 4. The formation of KA and NaA in the sap raises its osmotic pressure and water enters. 5. The concentration of potassium and sodium and the osmotic pressure become much greater inside than outside. For example, potassium may become 200 times as concentrated inside as outside. 6. No equilibrium occurs but a steady state is reached in which water and salt enter at the same rate so that the composition of the sap remains constant as its volume increases. 7. Since no equilibrium occurs there is a difference of thermodynamic potential between inside and outside. At the start the thermodynamic potential of KOH is much greater outside than inside. This difference gradually diminishes and in the steady state has about the same value as in Valonia. The difference in pH value between the internal and external solutions is also similar in both cases (about 2 pH units). 8. Accumulation does not depend on the presence of molecules or ions inside which are unable to pass out. One important feature of the hypothesis is not seen in the model: this is the exchange of HCO3 for Cl-. Experiments on this point are in progress.

scholarly journals Dietary Advanced Glycation End Products: Digestion, Metabolism and Modulation of Gut Microbial Ecology

Nutrients ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 215 ◽  
Author(s):  
Matthew Snelson ◽  
Melinda Coughlan
Keyword(s):  
Gut Microbiota ◽  
Advanced Glycation End Products ◽  
Short Chain Fatty Acids ◽  
Current Evidence ◽  
Advanced Glycation ◽  
Conflicting Evidence ◽  
Glycation End Products ◽  
End Products ◽  
Pass Through ◽  
The Impact

The formation of advanced glycation end products (AGEs) in foods is accelerated with heat treatment, particularly within foods that are cooked at high temperatures for long periods of time using dry heat. The modern processed diet is replete with AGEs, and excessive AGE consumption is thought to be associated with a number of negative health effects. Many dietary AGEs have high molecular weight and are not absorbed in the intestine, and instead pass through to the colon, where they are available for metabolism by the colonic bacteria. Recent studies have been conducted to explore the effects of AGEs on the composition of the gut microbiota as well as the production of beneficial microbial metabolites, in particular, short-chain fatty acids. However, there is conflicting evidence regarding the impact of dietary AGEs on gut microbiota reshaping, which may be due, in part, to the formation of alternate compounds during the thermal treatment of foods. This review summarises the current evidence regarding dietary sources of AGEs, their gastrointestinal absorption and role in gut microbiota reshaping, provides a brief overview of the health implications of dietary AGEs and highlights knowledge gaps and avenues for future study.

scholarly journals Advanced Glycation End Products and Risks for Chronic Diseases: Intervening Through Lifestyle Modification

2017 ◽  
Vol 13 (4) ◽  
pp. 384-404 ◽  
Author(s):  
Chandan Prasad ◽  
Kathleen E. Davis ◽  
Victorine Imrhan ◽  
Shanil Juma ◽  
Parakat Vijayagopal
Keyword(s):  
Advanced Glycation End Products ◽  
Chemical Nature ◽  
Lifestyle Modification ◽  
Cell Types ◽  
Advanced Glycation ◽  
Disease States ◽  
Multiple Receptors ◽  
Lifestyle Choices ◽  
Glycation End Products ◽  
End Products

Advanced glycation end products (AGEs) are a family of compounds of diverse chemical nature that are the products of nonenzymatic reactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs bind to one or more of their multiple receptors (RAGE) found on a variety of cell types and elicit an array of biologic responses. In this review, we have summarized the data on the nature of AGEs and issues associated with their measurements, their receptors, and changes in their expression under different physiologic and disease states. Last, we have used this information to prescribe lifestyle choices to modulate AGE-RAGE cycle for better health.

scholarly journals SOME CONSEQUENCES OF THE THEORY OF MEMBRANE EQUILIBRIA

1925 ◽  
Vol 9 (1) ◽  
pp. 97-109 ◽  
Author(s):  
David I. Hitchcock
Keyword(s):  
Membrane Potential ◽  
Osmotic Pressure ◽  
Ionization Constant ◽  
Weak Acid ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Weak Base ◽  
Acid Base ◽  
Hydrogen Ion Concentration ◽  
Pass Through

In applying Donnan's theory of membrane equilibria to systems where the non-diffusible ion is furnished by a weak acid, base, or ampholyte, certain new relations have been derived. Equations have been deduced which give the ion ratio and the apparent osmotic pressure as functions of the concentration and ionization constant of the weak electrolyte, and of the hydrogen ion concentration in its solution. The conditions for maximum values of these two properties have been formulated. It is pointed out that the progressive addition of acid to a system containing a non-diffusible weak base should not cause the value of the membrane potential to rise, pass through a maximum, and fall, but should only cause it to diminish. It is shown that the theory predicts slight differences in the effect of salts on the ion ratio in such systems, the effect increasing with the valence of the cation.

scholarly journals New Ecological Solutions Involved in the Cleaning of a 19th Century Icon

2020 ◽  
Vol 10 (3) ◽  
pp. 1175
Author(s):  
Tudor Cosmin Iurcovschi ◽  
Viorica Vasilache ◽  
Ion Sandu ◽  
Marius Zaharia ◽  
Olga Pintilie ◽  
...  
Keyword(s):  
Thin Layer ◽  
19Th Century ◽  
Analytical Methods ◽  
Room Temperature ◽  
Chemical Nature ◽  
Conservation Status ◽  
Licorice Root ◽  
Extraction Processes ◽  
New System ◽  
Made In

Cleaning of old icons requires special attention to selecting the processes and systems compatible with the chemical nature and adhesions of the deposits, to not affect the polychrome layer or their conservation status. The study was carried out on a 19th century icon made in fat tempera, on a thin layer of preparation that presents fouling. The cleaning was done using extracts obtained from sage, St. John’s Wort, and, respectively, licorice root teas obtained through different extraction processes: microwave, ultrasound, boiling, and room temperature, respectively. The washing capacity of the new system used was analyzed by analytical methods of assessing the cleaning degree: UV-Vis reflection, reflective colorimetry type CIE L*a*b*, co-assisted with optical microscopy and scanning electrone microscopy (SEM-EDX).

Prostaglandin synthesis by microsomes of circular and longitudinal gastrointestinal muscles

1983 ◽  
Vol 244 (4) ◽  
pp. G442-G448 ◽  
Author(s):  
K. M. Sanders ◽  
T. E. Northrup
Keyword(s):  
Arachidonic Acid ◽  
Small Bowel ◽  
Thin Layer ◽  
Enzyme Concentration ◽  
Prostaglandin Synthesis ◽  
Dependent Manner ◽  
End Products ◽  
Layer Chromatography ◽  
Dose Dependent ◽  
Longitudinal Muscles

Experiments were performed to determine whether longitudinal and circular muscles from various regions of stomach and small bowel had the capacity to convert arachidonic acid (AA) to prostaglandins (PGs). PG production by the microsomal fractions of isolated muscles was assayed by determining the conversion of [14C]AA to 14C-labeled 6-keto-PGF1 alpha, PGF2 alpha, PGE2, PGD2, PGA2, and thromboxane B2. Individual PGs were identified by thin-layer chromatography. The metabolism of [14C]AA to [14C]PGs was linearly related to substrate concentration, enzyme concentration, and incubation time at 37 degrees C and was inhibited in a dose-dependent manner by indomethacin. Longitudinal and circular muscles from all tested regions (corpus, fundus, antrum, pylorus, duodenum, jejunum, and ileum) synthesized PGs. In all regions the major end products of AA metabolism were 6-keto-PGF1 alpha, PGE2, and PGF2 alpha. The data indicate that circular and longitudinal muscles from all regions of the stomach and small bowel contain the enzymatic apparatus necessary to convert AA into prostaglandins.

Determination of the osmotic pressure of latex dispersions by a thin layer centrifuge method

1986 ◽  
Vol 18 (2-4) ◽  
pp. 283-291 ◽  
Author(s):  
Tibor Gilányi ◽  
Géza Horváth-Szabó ◽  
Ervin Wolfram
Keyword(s):  
Thin Layer ◽  
Osmotic Pressure ◽  
Centrifuge Method ◽  
Latex Dispersions

scholarly journals The properties of colloidal systems. III.—The osmotic pressure of electrolytically dissociated colloids

1911 ◽  
Vol 84 (571) ◽  
pp. 229-254 ◽  
Keyword(s):  
Osmotic Pressure ◽  
Congo Red ◽  
Chemical Nature ◽  
Dibasic Acid ◽  
Single Molecules ◽  
Strong Acid ◽  
Sodium Content ◽  
Disodium Salt ◽  
Colloidal Systems ◽  
Satisfactory Explanation

In a previous paper I showed that the osmotic pressure of solution of Congo red, as measured directly in an osmometer with a membrane of parchment-paper, is about 90—95 per cent. of that which they should have if the dye were present as undissociated single molecules, such as those of glucose or urea. Attention was chiefly directed, in the paper referred to, to the fact that a body behaving as a colloid gives as high an osmotic pressure as if it existed in solution as single molecules and not as aggregates. It is to be remembered, however, that Congo red is the sodium salt of a fairly strong acid and as such must be dissociated to a considerable degree in solutions of the concentration employed. On this account, the interpretation of the experimental results required further work. Subsequent investigations have shown that there are many difficulties in the way of a satisfactory explanation. As will be seen later, the close correspondence between the osmotic pressure found and that of the dye if undissociated must be due to the chemical nature of this particular dye as a disodium salt of a dibasic acid. Other dyes of a similar constitution, but of different sodium content, such as Chicago blue, do not shoe this property. I regard it as a somewhat unfortunate accident that Congo red was chosen as the object of the first investigation. Attention was thereby diverted from the more essential facts. As it will frequently be necessary to refer to the osmotic pressure as it would be shown by a body present in solution in undissociated single molecules, I propose, for convenience, to speak of it as the “molecular” osmotic pressure, although of course the expression is not strictly correct.

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