摘要:

RéSumé1.Caroténoïdes. Ces pigments sont beaucoup moins stables qu'on ne le croyait il y a quelques années. Ils s'isomérisent spontanément, s'oxydent en milieu alcalin et se dkcomposent en milieu acide. Ils se trouvent surtout dans les glandes sexuelles et les œufs des Invertébrés et y jouent peut‐être un rôle biologique important.2.Quinones. Les pigments d'oursins isolés récemment (échinochrome, spino‐chrome et autres) sont des oxy‐naphtoquinones. L'échinochrome, sécrété par les œufs dArbaciu, active les mouvements des spermatozoïdes et les attire vers l'œuf. Les naphtoquinones méritent un grand intérêt biochimique depuis que l'on sait qu'ils peuvent agir comme vitamine K (antihémorragique).Les pigments des Aptéres du genreCoccus(cochenille, kermès et acide laccaïnique) sont des dérivés de l'anthrachinone. Leur rôle biologique est inconnu.3.Pigments pyrroliques. (a) Porphyrines. II existe chez le LamellibranchePteria radiataune porphyrine caracteristique, la conchoporphyrine, qui est en quelque sorte un intermédiaire entre l'uroporphyrine et la protoporphyrine. Des porphyrines colorent en outre le tégument de quelques Vers.(b) Pigments biliaires. Les Invertébrés contiennent souvent la biliverdine ou des pigments analogues. Nous décrivons en détail plusieurs pigments spécifiques appartenant plus ou moins étroitement aux pigments biliaires. Ce sont: la rufine du tégument de la limace rouge,Arion rufus, la rufescine de la coquilled'Huliotis rufescens, les pigments bleu‐verts de la coquilled'Huliotis californiensis, la calliactine de 1'AnémoneSagurtia parasitica, les pigments violets de la sécrétiond'Aplysiaet un pigment vert des ailes de Lépidoptères.(c)Dérivésde la chlorophylle. Les colorations vertes des Invertébrés peuvent être dues soit à des algues symbiotiques, soit à la présence de chlorophylle alimentaire, soit à des pigments spécifiques résultant d'une transformation de la chlorophylle. Parmi ces derniers, la bonelline, pigment du VerBonellia viridisest le plus intéressant; c'est une mésochlorine naturelle. Plusieurs autres espèces de Vers contiennent des pigments tégumentaires verts peu étudiés.4.FZuvines. Pour les Insectes, la lactoflavine est unk vitamine comme pour les Vertébrés. Elle s'y trouve accumulée surtout dans les tubes de Malpighi.5.Ptérines. Ces pigments sont répandus surtout chez les Insectes. Les plus importants sont: la leucoptérine des ailes du Piéride du chou, la xanthoptérine des ailes deGonepteryx rhamniet du tégument des gutpês, et l'érythroptérine des taches rouges des ailesd'Euchloe cardamineset autres. Ce sont des dCrivCs de la purine. Les ptérines ne sont pas des produits d'excrétion; elle prendraient part au métabolisme azoté.6.Méanines. Ces corps ne se prêtent que difficilement à 1'étude chimique. Ils se forment par action de la tyrosinase, ferment contenant du cuivre. Le VerHalla parthenopaeacontient un pigment rouge, I'hallachrome, que l'on peut considirer comme stade intermédiaire de la formation de milanines à partir de la tyrosine. Unautreproduit intermédiaire serait le pigment violet de la rétinedes Céphalopodes.7.Pigments divers. (a) La pourpre de certains Gastéropodes est un dibromoindigo; le pigment est sécrété sous forme d'un chromogéne incolore qui se transforme en pigment par action de la lumière.(b) Lespigments indicateurs de pHsont très répandus chez les Inverté

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1940.tb00759.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

Summary1. The uniform series of chromosome movements we know as meiosis (pairing, torsion, reproduction, crossing‐over, co‐orientation, segregation) can now be placed in a causal sequence. This serves two purposes: to be tested as a working hypothesis and to be applied to the understanding of the characteristic variations of which meiosis is susceptible.2. Comparison of mutants, hybrids and other genetically controlled variants shows that these variations arise from three main sources: (i) the point at which the pairing chromosomes make contact; (ii) the time available for pairing; (iii) the amount of torsion capable of being developed in the parts of the chromosomes which are paired.3. All species are, as such, characteristically co‐ordinated with regard to these variables. They may be classified as procentric (Mecostethus) or proterminal (Chry‐sochruon) in the initiation of pairing. This difference affects the relative frequency of crossing‐over in chromosomes of two main types, with the centromere near an end and away from it (Fritillariu, Lilium).4. Exceptional cells, and individuals arising by segregation from hybrids, show that co‐ordination within the cell and the individual is not physiologically inherent in meiosis. Unco‐ordinated behaviour can take place in regard to all three prime variables (Allium, LiliumandTrillium).5. The time limit to pairing may be imposed artificially by heat treatment or X‐raying. We then have artificial localization of crossing‐over (Uvularia, Vicia).6. The amount of torsion depends on the speed of pairing and this in turn on the size of the nucleus. Doubling the chromosome number therefore reduces the crossing‐over frequency (Primula, Allium, Solanum, etc.).7. The preservation of torsion depends on the early contact of a chromosome at two points. The more numerous contact points of triploids therefore increase their frequency of crossing‐over per unit length paired, at the same time changing its distribution (Fritillaria, Tulipa, Drosophila).8. All species hybrids are structural hybrids. Their pairing is therefore slower and is cut short by the time limit. Hence their crossing‐over is reduced and relatively localized, unless the extreme of localization has already been reached in the parents (Triticum, Lilium).9. The study of the three prime variables is therefore necessary for the understanding of the causal sequence of meiosis and of the conditions of stability a

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1940.tb00760.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

Summary1. Fluorescence microscopy is based on the principle of illuminating the microscopic object by fluorescent light produced in the object itself. This must either contain fluorescent pigments or must be prepared for the purpose by a previous injection of fluorescent dyes. The fluorescence is excited by light rays of short wave‐lengths which are focused on to the object from a special source of light. Fluorescence microscopy can often be employed most fruitfully where microscopy in ordinary white light is inapplicable, particularly in the following fields of research: (a) for the detection of spontaneously fluorescent pigments and the examination of their distribution in the tissues in translucent and opaque objects; (b) for translucent objects treated with fluorescent dyestuffs, in which case fluorescence microscopy may render visible structures which cannot be observed in white light; (c) for the microscopic investigation of processes in living organisms which have previously been injected with suitable fluorescent dyes (intravital microscopy).2. Two fundamentally different types of fluorescence microscopes are in use, one using transmitted light for translucent objects, the other using incident light for opaque objects. As primary source of light lamps rich in light of 300–400 mμ and of great intrinsic brightness are used. The light beam is cooled by water and is then freed from the visible and infra‐red rays by suitable filters.For fluorescence microscopy in transmitted light the ultra‐violet beam is collected by a quartz condenser and projected on to a totally reflecting quartz prism which deflects the beam into a quartz Abbe condenser fixed in the substage of an ordinary microscope.For fluorescence microscopy in incident light two types of illumination are used: inside and outside illumination. In the former the microscope tube is fitted with a side tube through which the ultra‐violet beam is projected by a quartz condenser on to a totally reflecting prism or plate. These are fixed in the microscope tube so that they deflect the beam into the objective which acts simultaneously as condenser. In the outside illumination type the ultra‐violet beam is focused on to the object either unilaterally by lenses or mirrors or from all sides by mirrors. For fluorescence microscopy in incident light, stands with vertically movable stages are essential. For the inside illumination type, objectives are made from glass readily permeable to wave‐lengths of 300–400 mp. For all types, objectives must be free from. fluorescent material. For intravital microscopy only water immersions are used, which are constantly irrigated with a physiological salt solution. In all types trap filters have to be used to keep away from the eye any traces of the primary light.3. For fluorescence microscopy in transmitted light the object must be prepared without using any fluorescent mounting material. Objects which do not contain fluorescent pigments have to be treated with fluorescent dyes, a large number of which has been described for this purpose.For intravital microscopy animals must also be treated with fluorescent dyes, fluorescin and acriflavin being most suitable. The former allows a simultaneous estimation of thepHof the tissue.4. Photomicrographs of the fluorescent image in black and white as well as in colour can be obtained both from inanimate and from living objects. In the latter case the correct fixation of the object is the most difficult problem. Much care is also necessary to prevent the slightest trace of the primary light passing into the camera.5. By using a spectral eyepiece it is possible to identify a fluorescent pigment present in the tissue by examination of the emission bands of the fluorescent light.6. The fluorescence microscopic examination of unstained objects has led to the detection and isolation of natural fluorescent pigments, as in the case of lyochromes (riboflavin, vitamin BJ, and to the observation of the distribution of fluorescent pigments in animal and plant tissues (chlorophyll, porphyrins, lyochromes, vitamin A).No results of great importance have so far been obtained by applying fluorescence microscopy to normal or pathological tissues stained with fluorescent dyes.Valuable results have been gained by fluorescence microscopy in the study of the mechanism of the effect of fluorescent chemotherapeutics on parasites and in bacteriology. The study of virus bodies might become a particular successful field for the method.Intravital microscopy has been successfully applied to the investigation of the physiology and pathology of animal and plant organs, particularly in dealing with the function of various glands and body fluids.7. Fluorescence microscopy of tissue sections, smears, or other translucent preparations has two primary purposes:(a) In unstained preparations it allows of the recognition and localization in animal and plant tissues of spontaneously fluorescent substances which cannot be discovered by any other methods. Here the method will probably have a great future.(b) In preparations treated with fluorochroms it is a new method of staining, the value of which is, however, not greater than that of other staining methods, though it has led to important results in special cases, as in the localization of chemo‐therapeutics acting on parasites.In intravital microscopy which uses fluorescent microscopy only as a means to an end, we have, however, a method which has opened a new field for research, as it permits the observation of biological processes occurring within living organs and cells by extending the two‐dimensional pictures of the usual microscopy into three dimensional space and adding the fourth dimension of time. The results gained up to now should represent only the beginning of a new and promisin

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1940.tb00761.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1940.tb00762.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

SummaryFishes and, in lesser degree, Amphibia respond to backgrounds in such a manner that their shade, and to a certain extent their colour, tend to conform to that of the substratum on which they lie, or over which they swim. The integrity of the eyes and of major portions of the nervous system is essefitial to these phenomena.The immediate, transitory or “physiological” dour changes are due to the rearrangement of pigment particles already present. When the effective stimuli are continued for some days or weeks, changes become evident both in the number of chromatophores and in the pigment contents of each (quantitative or “morphological” colour changes).All three of the types of chromatophores (melanophores, guanophores, lipo‐phores) are affected by these changes. Dark backgrounds favour the production of melanin and inhibit the production of guanin. Pale backgrounds have a reverse effect. In fishes at least, production (or retention) of the yellow pigment xantho‐phyll is favoured by black backgrounds and retarded by white ones, agreeing thus with melanin. To what extent there is any specific effect ofcolouredbackgrounds (sensu stricto) upon the quantity of xanthophyll is not clear at present.Intensity of illumination, above a rather low level, has very little effect upon pigment formation in fishes. There is some evidence, however, of a slight degree of positive correlation between light intensity and melanin formation. Total darkness leads to pigment reduction both in fishes and Amphibia.Blinding of both eyes, in both of these groups, results in a marked increase of melanin, but only in animals which are kept in the light.Experiments involving illumination from below are known to have resulted in considerable increases in pigmentation of the ventral surface, both in fishes and Amphibia. It is not certain in these cases whether optic stimuli have been concerned, or whether the effects have been due to direct illumination of the skin.The response of a fish to its background is primarily a response to albedo, this being defined as the proportion of incident light which is reflected or dispersed from a given surface. On the basis of considerable evidence, a rule has been formulated which has been found to hold approximately, at least for certain fishes. This rule is that, when the animals are subjected to a variety of backgrounds, under uniform illumination, the amount of melanin (or the number of melanophores) produced varies inversely as the logarithm of the albedo of the background. The close analogy between these pigmentary responses of fishes, and the phenomena of sense perception in man for which the “Weber‐Fechner Law” was formulated was pointed out.The question of how a fish recognizes, and responds to, a given albedo, regardless of the absolute degree of illumination present, resolves itself into the question as to how the animal perceives the ratio between the source of light and the light reflected from the bottom and surrounding objects. This last does not seem to be so difficult an achievement when we consider that the ratio in question is ordinarily that between the upper and lower halves of the field of vision, or in other words, between the stimulus received by the lower and upper halves of the retina. Experimental evidence is accumulating showing that these two areas of the retina are functionally differentiated in the required manner.It was early recognized that those conditions which tend to bring about transitory colour changes are the same ones which, if prolonged, produce quantitative changes. The question has been raised whether the state of chromatophore “expansion” (pigment dispersal)per se, promotes pigment production and cell multiplication, and chromatophore “contraction” promotes the reverse processes, or whether both transitory and quantitative changes are the results of a common (probably hormonal) cause. The weight of present evidence probably favours the latter interpretation.The relative roles of direct nervous control of the chromatophores and control through hormones is still a subject of controversy, both for fishes and Amphibia. It now seems probable, not only that these two classes of animals differ from one another in important ways, but that the two major groups of fishes, elasmobranchs and teleosts, likewise differ from one another. Even within the group of elasmobranchs, moreover, important differences have been claimed. The whole subject is further complicated by the discovery that “direct” nervous control is itself probably mediated through hormones liberated by the nerve terminals. In general, it is now helieved that nervous control (with the reservation just indicated) is the one chiefly involved in the colour changes of teleosts, while control through blood‐borne hormones is chiefly involved in the colour changes of both elasmobranchs and Amphibia. But this statement oversimplifies t

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1940.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1940.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY