Low Molecular Weight Constituents Research Articles

Regulatory function of a primitive vertebrate kidney

1. 1. Determinations were mae of the major low molecular weight constituents of serum and urine of Pacific hagfish ( Eptatretus stouti) and of the sea water in which they were kept. 2. 2. The concentrations of sodium and chloride, and probably the osmotic pressure, of serum and urine were the same. 3. 3. Concentrations of potassium, magnesium, sulfate and phosphate were greater in urine than serum, indicating that these ions are secreted into the glomerular filtrate by the mesonephric duct cells. 4. 4. Concentrations of calcium and glucose were lower in urine than in serum. This is interpreted as a reabsorption of glucose by the mesonephric duct cells. Some of the plasma calcium is bound to proteins and is not filtered through the glomeruli, accounting for the low level of urine calcium. 5. 5. It is suggested that hydrogen-ion activity of the plasma is regulated in the kidney. 6. 6. Experiments with C 14-labeled inulin showed that water is not reabsorbed from the glomerular filtrate. This indicates that there is no renal mechanism for the active reabsorption of sodium ions, a lack that is unique among vertebrates. 7. 7. The lack of renal sodium reabsorption, which was requisite for the invasion of fresh water by vertebrates, is regarded as a primitive omission rather than a secondary loss. This strongly suggests that myxinoid ancestors have always been marine and, therefore, that vertebrates must have originated in the sea. 8. 8. The cationic concentrations in hagfish slime are compared with the concentrations in serum and cells. Slime may function in the extra-renal secretion of calcium, magnesium and potassium.

Spectroscopic investigations of lignin, humic substances and peat

The close structural and genetic relationships between lignin, humic substances and further products of the coalification process, often supported by strong arguments and well-based considerations, is generally accepted. Such relationships can be particularly well demonstrated by absorption of light by these substances in the ultraviolet and visible regions (250–700 mμ), in the near infrared (0.7–2.5 μ), and finally in the infrared region of the NaCl-prism (2–14 μ). In fact, the similarity among these substances also became apparent in the general gradation of these spectra; such gradation may take on particular significance if interpretation of the spectra is to be used for genetic, chemical, or even physical studies. In any case, if it is recognized that the spectra have different sources in different regions, then the spectra of individual regions must be very different. In some cases, special atomic groups are associated with characteristic bands, and in many instances additional use of the near infrared region (harmonics) can be useful. Ultraviolet spectra are usually completely uncharacteristic, with absorption intensity dropping in going from shorter to longer wavelengths. Nevertheless, the general impression of the ultraviolet spectrum, along with other prominent maxima and minima from other spectra, and additional analytical data permit a certain delineation in the lignification-humification-coahfication sequence. Therefore, it is obvious that it is necessary to study the materials in question over the entire accessible region of light absorption. As a further point, it should be noted that a spectrum is frequently difficult to interpret and become useful only when a reference material can be used. The intermediate position of humic substances is not surprising inasmuch as they certainly arise from lignin, judging from the decomposition products of lignin, and, moreover, its natural conversion in the coalification process leads first to peat and the usual related substances. The particularly uncharacteristic ultraviolet spectrum of humic substances should be noted. If reactive acidic complexes (humic acid precursors) can be separated from the true, essentially unreactive humic acids, then it should be possible to determine their differences experimentally by absorption techniques using suitable preparations. If this study could then be generalized, it might illustrate that the further advanced a material is in the course of this natural process, the more uncharacteristic its ultraviolet spectrum becomes. A number of maxima in the ultraviolet spectrum were taken as being characteristic for lignin, and in this way the substance could be differentiated from humic acid; the humic acid precursors gave the same general impression. It should be noted that for many lignins there is a displacement of certain maxima dependent upon pH, an effect that is not generally noted for humic acid precursors. The spectrum for lignin also shows a general decrease in the intensity of light absorption with increasing wavelength. As already stated, infrared spectra are particular informative. For the materials in question, characteristic groups can be identified in spite of a more or less marked background absorption. Thus, the fewer the number of bands in the infrared spectrum or the further along the material is in the coalification process, the more intense the background absorption becomes. Attempts are being made to define most low molecular weight constituents that do not at the outset enter into the lignification or humification process and to compare their absorptions with those for lignin or humic substances. These materials may play a special key role in the alteration of lignin or humic substances and there is also the possibility that something may be learned about the nature of their bonding with lignin or humic substances. It is felt that if these questions are answerable by the application of spectroscopic techniques, that later a solution to the overall picture may be attainable.

Changes in Carbohydrate, Protein, and Non-Protein Nitrogenous Compounds of Developing Wheat Grain

Analyses were carried out on the main morphological parts of grain of Triticum. vulgare and of T. durum during development from a 'few days after flowering to maturity. The low molecular weight constituents (non-protein nitrogenous com. pounds, sucrose, reducing sugars, and .x-keto acids) decreased in concentration but the amounts per grain remained relatively constant during development. However. the macromolecular materials (starch, pentosans, and protein) increased in concentration and in amount per grain. Metabolism of developing endosperm is discussed in relation to these observations.

Studies on Myxine glutinosa—I. The chemical composition of the tissues

1. (1) Determinations were made of the concentrations of the major low molecular weight constituents in serum, muscle and liver of Myxine glutinosa L. (the Atlantic hagfish). 2. (2) The intracellular concentrations of the above substances have been calculated using the inulin space as a measure of the extra-cellular fluid compartment of the tissues. 3. (3) The concentrations of potassium, sodium and chloride in the intracellular water were 140–200, 110–150 and 100–120 mM/kg respectively. For potassium the ratio of the intracellular to extracellular concentration was 12 : 1. The corresponding ratio for sodium was 1 : 4·5. 4. (4) From the composition of the various tissues it is likely that serum and cells had the same osmotic pressure as sea water. Serum contained mainly inorganic ions and the intracellular fluid contained approximately equal quantities of inorganic and organic constituents. 5. (5) The major intracellular organic compounds were amino acids (20–70 mM/kg H 2O), trimethylamine oxide (211–230 mM/kg H 2O) and an unknown acidic substance about 200 mM/kg H 2O).

Action of Solvents on Dried Linseed Oil Films

THE action of a range of organic solvents on aged linseed oil films, both pigmented and unpigmented, has been investigated1. A specially designed apparatus based on the parallel plate viscometer was used2 to make precise measurements of changes in thickness of films coated on a rigid substrate, while free films (these proved to be isotropic in behaviour) were observed under a measuring microscope. The results thus obtained, together with related gravimetric measurements, made it possible to determine rates of swelling and deswelling, and to examine the characteristics of the leaching process in which constituents of low molecular weight are removed when the felt-like structure is swollen.

Sur la constitution du “cord factor” isolé d'une souche humaine de bacille tuberculeux

The “cord factor” of a streptomycin-resistant mutant of H37-Rv has been purified by chromatography; the nearly colourless wax, m.p. 42–44°, [ a] J = +30°, thus obtained has an elementary composition corresponding to the formula C 95H 189O 9N ± 5CH 2 ± O. Alkaline saponification of this “cord factor” liberates one molecule of mycolic acid C 87H 174O 4 ± 5CH 2. The presence of a carbohydrate constituent is indicated by colour reactions. These results are in agreement with those of Noll and Bloch 4 who have identified one molecule of mycolic acid and one molecule of D-glucose in the “cord factor” of another human strain. A third, low molecular weight constituent containing a tertiary nitrogen, has not yet been identified.

Preparation of polyasparaginic acid (polyaspartic acid) by the thermal autocondensation of asparaginic acid

Aspartic acid changes on being heated without solvents to a not completely uniform substance of anhydride character. This appears to have a structure II different from that assigned to it by earlier investigators. Mild hydrolysis produces a mixture of polyaspartic acids which has been freed by dialysis from constituents of low molecular weight leaving a polypeptide with the approximate molecular weight of 8,200. It is presumed that this polyaspartic acid, differing from the known synthetic α-polyaspartic acid, closely approximates to the β-polyaspartic acid of structure IV.