摘要:

SummarySpectrographic methods which are applicable to the analysis of plants and soils include those employing flame, arc and spark excitation. Some seventy elements can be determined spectrographically, the most important exceptions being gaseous and non‐metallic elements.The most widely used flame emission method is that devised by Lundegårdh, in which the solution under examination is sprayed into an air‐acetylene flame. This method is particularly suited to the determination of the alkali and alkaline earth metals in soil and plant extracts. The Ramage method, in which the material is introduced on a paper spill, has also been used to some extent.Arc methods are widely employed for the determination of both trace and major constituents, generally with solid material in carbon or graphite electrodes of a shape chosen to suit the object of the investigation. The most sensitive source for most elements is probably the cathode‐layer arc, although the high‐voltage a.c. arc is useful for certain elements in solution. Interrupted arc and spark sources have been less widely used but have advantages for certain purposes, such as the determination of boron.Some direct photometric methods, omitting the use of a photographic plate, are described.Spectrographic methods are applicable to qualitative, semi‐quantitative or quantitative determinations. Semi‐quantitative methods generally employ a visual or subjective assessment of the content of an element, and are useful in giving a general indication of the levels of most of the trace constituents present in any sample, with an accuracy of some 30%. When objective photometric measurements are used, figures reproducible to ± 3–10% may be expected, depending on the method employed and the element being determined.Applications of spectrographic methods to analyses of soils and plants have been along both lines, either the semi‐quantitative survey of as many elements as possible, or the quantitative determination of specific elements. Attention is drawn to the relationship of the soil content to the geological origin of its parent material and to soil effects which may influ

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1947.tb00556.x

出版商:Blackwell Publishing Ltd    

年代:1947

数据来源: WILEY

摘要:

Summary1. The characteristic histological feature of the pars nervosa is a dense network of nonmyelinated nerve fibres, which end within the pars nervosa and not in relationship to glandular cells of the pituitary. These fibres originate in the supraoptic and paraventricular nuclei of the hypothalamus and pass through the median eminence into the pituitary stalk.2. The antidiuretic, pressor and oxytocic activities of extracts of the posterior lobe of the pituitary are derived from the pars nervosa and not from the pars intermedia. Despite similarities in anatomical structure between the tissues of the tuber cinereum, pituitary stalk and pars nervosa, extracts of stalk and tuber cinereum have very little pharmacological activity, so that the only established source of pituitary antidiuretic substance is the pars nervosa itself.3. The antidiuretic action of extracts of the posterior lobe is described, and it is emphasized that this action is only demonstrable when there is rapid secretion of dilute urine, as in water diuresis in the intact animal, in diabetes insipidus and in perfused kidneys. The antidiuretic action is produced by very small amounts of the extract.4. In order to prove that the antidiuretic substance is a true hormone, the evidence for its release into the circulation during life is examined. The tests available for the detection of antidiuretic activity are not adequate to allow the demonstration of antidiuretic substance in the body fluids; but it has been conclusively established that the inhibition of water diuresis which may occur in the unanaesthetized dog from emotional stress or from the intravenous injection of acetylcholine, morphine or nicotine is mediated by the release of antidiuretic hormone from the pars nervosa.5. It has long been believed that clinical diabetes insipidus is due to deficiency of antidiuretic hormone; in sT V the results on the fluid exchange of experimental lesions in the pituitary region are examined. Permanent diabetes insipidus regularly results from section of the supraoptico‐hypophyseal tracts in the median eminence, and as the result of the section there is atrophy and loss of function of the pars nervosa. However, operative removal of the posterior lobe causes only a temporary increase in the fluid exchange, but permanent diabetes insipidus has resulted in some instances where the posterior lobe, stalk and part of the tuber cinereum were removed. It is usually accepted that the stalk and tuber cinereum as well as the pars nervosa are significant sources of the antidiuretic hormone, and that diabetes insipidus only occurs when these three parts of the neurohypophysis are removed or atrophied, but there is only limited evidence in support of this explanation. The relation of the anterior lobe to the production of diabetes insipidus is also discussed.6. Thus, there are three lines of evidence which justify the acceptance of the pars nervosa as controlling the rate of urine secretion by means of its antidiuretic hormone: the antidiuretic activity of extracts, the release of antidiuretic hormone during emotional stress, and the association of diabetes insipidus with loss of the function of the pars nervosa.7. The evidence is inadequate to‐establish other suggested functions of the mammalian pars nerv

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1947.tb00557.x

出版商:Blackwell Publishing Ltd    

年代:1947

数据来源: WILEY

摘要:

SummaryThe underlying unity between the normal growth requirements of micro‐organisms and those of animals is pointed out, and the wide range of organisms requiring unidentified members of the vitamin B complex is given.The preparation and chemical properties of a number of these unknown factors is described. The biological activity of many of these compounds has been assessed by their growth‐promoting properties forLactobacillus caseiE andStreptococcus lactisR. On this basis three compounds known as the norite eluate factors (orL. caseifactors) have been prepared from liver, yeast and fermentation residues with similar chemical properties but differing activity for these micro‐organisms. A synthetic material of undisclosed structure has been described and is claimed to be identical with the compound isolated from liver. From this work and that concerning folic acid, a factor obtained from spinach, it appears that there are a number of naturally occurring substances which bear a close chemical resemblance, but slight changes in structure cause considerable changes in biological activity.A factor (vitamin Bc) has been obtained from liver which is active forL. caseiE andS. lactisR and for normal growth, feathering and haematopoiesis in the chick, but its identity with any of the above factors is not proved. A more complex form of this substance has been obtained which is active for the chick but not for the micro‐organisms. A factor 2500 times more active forS. lactisR than forL. caseiE has been obtained from an unstated source.A factor (vitamin M) which cures nutritional cytopenia in monkeys has been prepared from liver and yeast, and this material can be converted into anS. lactisR‐stimulating factor. Vitamin Bc, vitamin M,L. caseifactor and folic acid are probably closely related, and some interrelationships in biological activity have been demonstrated.The total growth requirements ofL. caseiE and certain strains ofCorynebacterium diphtheriaefor unidentified factors have been studied by other workers, as distinct from the attempted isolation of any one of them, and the existence of at least five factors required by these micro‐organisms has been described. Their concentration from liver and outstanding chemical properties have been detailed. Similarities between theC. diphtheriaefactor, strepogenin–a factor required by certain strains of haemolytic streptococci–and a factor required by certain strains ofS. lactisare apparent. It has been shown that different factors are required byL. caseiE for the initiation of growth and for the production of lactic acid, and the second of these materials has been shown to consist of at least three factors, one of which is related to folic acid and the synthetic material of the ‘norite eluate’ factors.Apparent discrepancies in growth requirements of the micro‐organisms probably arise from unrecognized impurities in basal media, the enforced use of concentrates of active factors or the employment of cultures of differing age, resulting in differing growth requirements.Further factors are described, including a fat‐soluble factor or factors stimulatory forL. caseiE, and factors distinct from those mentioned above, required by the chick and guinea‐pig.Finally, the relationships between the unidentified factors and known compounds, especially purines, pyrimidines and pterins, in the nutrition of micro‐organisms are discussed. A structural resemblance between xanthopterin and folic acid has been indicated, and it has been shown possible to replace folic acid and vitamin Bccompletely for 5.lactisR and partially forL. caseiE by thymine, together with one of several purines.I am greatly indebted to Dr F. C. Happold and Mrs D. E. Dolby for much helpful criticism during the

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1947.tb00558.x

出版商:Blackwell Publishing Ltd    

年代:1947

数据来源: WILEY

摘要:

Résumé1o. Le tableau 2 résume ce que l'on sait sur la présence ďacétylcholine et de cholinestérase chez les Invertébrés, ainsi que sur la sensibilityé. des tissus àľacétylcholine et aux poisons qui paralysent ľaction de cette substance.2o. La présence de nerfs cholinergiques est démontrée chez les Annélides (Armicolu, Aphrodite, Lumbricus, Hirudo), et les Siponculiens (Sipuncuh), chez les 1 Iolot huries, chez un seul mollusque (Venus mercenaria).3o. Ľexistence de nerfs cholinergiques est inconcevable chez les Cœntérés.4o. Chez les Arthropodes (Crustacés, Insectes et Arachnomorphes) tout porte à croire que les nerfs ne transmettent pas ľ'excitation par ľintermédiaire ľacétykholine.5o. Chez leo Mollusques, àľexception deVenus mercenaria, tous, les essais de démonstration de nerfs cholinergiques ont échoué.6o. Ľexistence de nerfs adrénergiques chez les Annélides est très probable, mais non encore certaine; de tels nerfs existent vraisemblablement chez les Céphalopodes et chez ľaplysie.7o. Le cmur et les tissus des Invertébrés manifestent pour ľadrénaline et les amines syrnpathicomimétiques une sensibi

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1947.tb00559.x

出版商:Blackwell Publishing Ltd    

年代:1947

数据来源: WILEY