Chromatophore

“ Most pigment-containing chromatophores (melanophores, erythrophores, xanthophores and cyanophores) are not only specialized in producing and storing, but also in translocating their numerous pigment particles [8] , [10] . They increase color visibility by radial particle dispersal or reduce it by concentric particle aggregation. In contrast to these pigment-based mechanisms, iridophores are chromatophores, which use refractive guanine platelets to create a silvery appearance or to generate structural colors (like most blue hues in fishes) [11] . ”

“ Scale bar = 500 μm.Spectra of excitation and emission of the fluorescent pigment in fluorescent chromatophores.Fluorescence has a maximum at around 595 nm (dashed line) with an optimal excitation wavelength around 500 nm (solid line) .Distribution of erythrophores, melanophores and fluorescent chromatophores in the interradial membrane of a dorsal fin of E. pellucida.a) Erythrophores (red) and melanophores (black) are visible in bright field microscopy. b) Fluorescent chromatophores appear in fluorescence microscopy. ”

“ Cell-wall firm not gelatinous, rarely forming colonies. Fore-end of the body with two or four (seldom five) flagella. Almost always green in consequence of the presence of a very large single chromatophore. Generally a delicate shell-like envelope of membranous consistence. 1 to 2 simple contractile vacuoles at the base of the flagella. Usually one eye-speck. Division of the protoplasm within the envelope may produce four, eight or more new individuals. ”

“ Order 5.—EUGLENACEAE. Vacuole large, a reservoir for one or more accessory vacuoles, contractile and opening to the surface by a canal (“pharynx”) in which are planted one or two strong flagella; pellicle strong often striated; nucleus large, chromatophores green, complex or absent; reserves paramylum granules of definite shape, and oil; nutrition variable; body stiff or “metabolic,” never amoeboid. Among the true Flagellates these are the largest, few being below 40 μ and several attaining 130 μ in length of cell-body (excluding flagellum) . ”

“ Under the influence of ATP, phosphoglyceric acid is synthesized and further built up by way of carbohydrate phosphates to hexose sugars and finally to starch. In many starchy fruits, a small proportion of phosphate remains attached to the end product.
The synthesis of proteins is under the control of deoxyribonucleic acid or ribonucleic acid, abbreviated by the symbols DNA and RNA. The genes in the nucleus are parts of a giant DNA molecule. RNA is a universal constituent of all living cells. Where protein synthesis is intense, the content in RNA is high. ”

“ Observation of the process of division of the nucleus (karyokinesis) in plants generally has shown (for details see Cytology) that the linin-reticulum of the resting nucleus breaks up into a definite number of segments, the chromosomes, each of which bears a series of minute bodies, the chromatin-disks or chromomeres, consisting largely of a substance termed chromatin. In the ordinary homotype divisions of the nuclei the characteristic number of chromosomes is always observable; but when the spore-mother-cells are being formed the number of chromosomes is reduced to one-half. ”

“ In either case the chromatin material that goes into the two cells is exactly alike, so that if the cells themselves become different there must have developed a difference in the protoplasm at the two ends of the cell from which they came. Our bodies are made up of millions of cells, of a great many different kinds, but however different they may be the chromatin of each exactly duplicates that of every other one, or did when the cells were first formed; there is reason to believe that the chromatin may become changed during the lifetime of the cells, at least in some cases. ”

“ Now (like sulphur, present in the albuminoid base) , phosphorus is an element which, besides having several allotropic forms, has a great affinity for oxygen; and an organic compound into which it enters, beyond the instability otherwise caused, has a special instability caused by its presence. The tendency to undergo change will therefore be great when the proportion of the phosphorized component is great. Hence the statement that "the chemical differences between chromatin and cytoplasm, striking and constant as they are, are differences of degree only;" ”

“ There are about ninety different games which electrons and protons can play, that is ninety different kinds of atoms. These games differ in the number of electrons and protons who play and in the way they arrange themselves. Larger games can be formed if a number of atoms join together. Then there is a “molecule.” Of molecules there are as many kinds as there are different substances in the world. It takes a lot of molecules together to form something big enough to see, for even the largest molecule, that of starch, is much too small to be seen by itself with the best possible microscope. ”

“ Chemical analysis associated with physical analysis by means of the polariscope, spectroscope, x-rays, ultramicroscope, etc. is extremely useful in determining the structure of inorganic units like the atom and the molecule. Both, too, throw valuable light on the problem of the structure of non-living multimolecules such as the crystal units of crystalloids and the ultramicrons of colloids, but they furnish no clue to the submicroscopical morphology of the living cell. ”

“ A very capital process for many purposes is to float or steep your paper in a mixed solution of bichromate of potash and sulphate of copper. As for E. Hunt's chromotype process,” 2 I have mixed gelatine, or occasionally grape sugar, or both, with the solution, but instead of developing it by a silver solution, as in the chromotype, wash out the salts unacted on by light, and develop by floating on a solution of ferrocyanide of potassium. ”

“ Should you be interested, we now have an article in press on the Journal of Cellular Physiology entitled: “Nucleic acid synthesis in the frog liver cell: A definitive study.” We have found substantial evidence which demonstrates that there is no interconversion of the two types of nucleic acid.
I cannot help but comment about your recent paper in Scientia—I do not believe that it is at all possible to devise computers which can handle the species of data which we obtain. Your data being less complex, of course, may fit. ”

“ Using the second blank chromatogram, subtract this chromatogram electronically from sam ple chromatograms. This improves the UV baseline of sample chromatograms and facilitates accurate integration of peaks in low level samples. Analyze one add itional so lvent blank within the sam ple se t. 10. Analyze a minimum of three field controls and three field blanks or at least one field control and one fie ld blank for every ten samples. Use the field controls and field blanks to identify non-isocyanate peaks (generally reagent artifact peaks) that are likely to appear in the samples. ”

“ In the majority of forms it has not hitherto been possible to demonstrate a nucleus of theNucleus. type which is so characteristic of the higher plants. Attention has accordingly been directed to the deeply-staining granules mentioned above, and the term chromatin-granules has been applied to them, and they have been considered to represent a rudimentary nucleus. That these granules consist of a material similar to the chromatin of the nucleus of higher forms is very doubtful, and the comparison with the nucleus of more highly organized cells rests on a very slender basis. ”

“ Hence, given the number of atoms in a molecule, and the valency of each atom, it became possible to calculate the number of different arrangements of these atoms which could be produced; and careful experiment has often succeeded in preparing all the different, theoretically possible, compounds. The difference of properties of such compounds, i. e., of compounds the molecules of which are constituted of the same number of the same atoms, but differently arranged, is attempted to be indicated in the "structural" or "rational" formulæ of modern chemistry. ”

“ Oxyhalogen derivatives of chromium are known, the oxychloride, CrO2Cl2, resulting on heating potassium bichromate and common salt with concentrated sulphuric acid. It distils over as a dark red liquid of boiling point 117° C., and is to be regarded as the acid chloride corresponding to chromic acid, CrO2 (OH) 2. It dissolves iodine and absorbs chlorine, and is decomposed by water with formation of chromic and hydrochloric acids; it takes fire in contact with sulphur, ammonia, alcohol, &c., and explodes in contact with phosphorus; it also acts as a powerful oxidizing agent. ”

“ Filter all samples, eluents, and water flowing through the ion chromatograph to avoid plugging system valves or columns. Transfer a portion of sample solution to a syringe fitted with an inline membrane filter, for direct injection or for transfer to autosampler vials. Inject 50-μL sample aliquot. For manual operation, inject 2 to 3 mL of sample from syringe (through inline filter) to ensure complete rinse of the sample loop. Measure peak height. If sample peak height exceeds the linear calibration range, dilute with eluent, reanalyze, and apply the appropriate dilution factor in calculations. ”

“ CHROMIC ACID AND SALTS. Chromic acid is rarely used alone in pathologic work, but is a constituent of Flemming’s solution (see below) . Its salts are employed in the form of:—
A. Müller’s Fluid (Potassium bichromate 25.0 grms., sodium sulphate 10.0 grms., water 1,000.0 cc.) This was formerly the favorite fixing solution, but is now used chiefly for the eye and nervous tissues, either alone, or after formol fixation, or mixed with formol. Large pieces may be used, even an entire brain, but the process requires months or even a year for the best results. Even small pieces take several weeks. ”

“ The alkaline chromates are soluble in water, those of most other metals being insoluble. By the addition of mineral acids, they are converted rapidly into bichromates. They are easily reduced in acid solution by sulphuretted hydrogen, and also by sulphur dioxide to chromium salts. The chromates are stable towards heat; they are poisonous, and may be recognized by the yellow precipitates they give with soluble barium and lead salts.
Potassium chromate, K2CrO4, may be prepared by neutralizing a solution of potassium bichromate with potassium carbonate or with caustic potash. ”

“ Thus, for example, an atom of carbon yields only one compound with four atoms of hydrogen and one with four atoms of chlorine in the molecule, whilst the atoms of chlorine and hydrogen unite only in the proportions of one to one. Simplicity is here evident, and forms a point of departure from which it is easy to move forward with firm and secure tread. Other elements are of a different nature. Phosphorus unites with three and with five atoms of chlorine, and consequently the simplicity and sharpness of the application of structural conceptions are lost. ”

“ The chromophore-auxochrome theory (Kauffmann) regards colour as due to the entry of an “auxochrome” into a “chromophoric” molecule. (3) If a colourless compound gives a coloured one on solution or by 72 salt-formation, the production of colour may be explained as a particular form of ionization (Baeyer) , or by a molecular rearrangement (Hantzsch) . A dynamical theory due to E.C.C. Baly regards colour as due to “isorropesis” or an oscillation between the residual affinities of adjacent atoms composing the molecule. ”

“ The easy transitions of the ortho-, meta-, and pyrophosphoric acids, by means of the hydrogen of ammonia, into the lower acids, and conversely, tend to complicate the study of this very large class of compounds, and it is rarely that the nature of a product thus obtained can be judged from its composition; and this all the more that instances of isomerism and polymerism, of mixture between water of crystallisation and of constitution, &c., are here possible. Many data are yet needed to enable us to form a true judgment as to the composition and structure of such compounds. ”

“ If the strength of an acid is expressed in percentage by weight, due regard must be paid to its specific gravity. For example, hydrochloric acid (sp. gr. 1.12) contains 23.8 per cent HCl !by weight!; that is, 0.2666 gram HCl in each cubic centimeter.
5. It is sometimes desirable to avoid the manipulation required for the separation of the constituents of a mixture of substances by making what is called an "indirect analysis." For example, in the analysis of silicate rocks, the sodium and potassium present may be obtained in the form of their chlorides and weighed together. ”

“ With dilution of the calibration stock solution in eluent solution, prepare calibration working standard solutions covering the range of approximately 0.4 to 4 mg/L of chloride, bromide and nitrate. Store working standards in tightly sealed polyethylene bottles. Prepare fresh working standards weekly. 15.
Calibrate the ion chromatograph with at least six working standards covering the range of 0.4 to 4 mg/L of chloride, bromide and nitrate per sample by preparing a calibration graph of anion peak height (mm or μS [micro-siemens] ) vs. concentration (mg/L) . ”

“ There is no dry assay for phosphorus. All assays for it are made either gravimetrically or volumetrically.
The separation of phosphoric oxide is made as follows:—The ore or metal is dissolved in acid and evaporated, to render the silica insoluble. It is taken up with hydrochloric acid, diluted with water, and treated with sulphuretted hydrogen. The filtrate is boiled, to get rid of the excess of gas, and treated with nitric acid, to peroxidize the iron present. ”