摘要:

Summary.The foregoing article is an attempt to give a general account of the growth factors of lower organisms,i.e. the substances which must be supplied in addition to food materials of known composition in order that normal growth can occur. As regards the growth factors required by lower organisms, the number of cases to which such a strict definition can be applied is limited to a few, and it has been necessary to include discussion of factors of which the indispensable nature is uncertain. In the case of growth factors used by higher organisms, discussion has been limited to a consideration of vitamins which are all, by definition and common usage of the term, essential. In most instances the chemical composition of growth factors is unknown.In order to give the biological reader as general a view as possible the author has included an account of some of the more important experimental details which may influence growth—not necessarily growth factors in the strict sense—though these should be already well known to specialists in the field under review. These influences may be connected with chemical substances in the culture medium,e.g. inhibitory substances, carbon dioxide, amino acids, salts; or with its physicochemical properties,e.g. surface tension,pH, oxidation‐reduction potential. Further, a discussion is included of two important points connected with the organism itself, viz. size of seeding and cultural characteristics (Section II).There is evidence for the existence of growth‐stimulating factors in the case of most of the organisms which have been studied. Often proof has been lacking of the absolute necessity of such factors for growth, and it is true to state that much of the work that has been carried out, beyond showing that growth of an organism can be improved by addition of certain materials, has added little to our real knowledge of the problem. More detailed knowledge of indispensable factors has been obtained in the case of some of the Coccaceae, Bacteriaceae (tribe Haemophileae), Mycobacteriaceae, Chlamydobacteriaceae and Fungi. In the Bacteria (Schizomycetes) the organisms which have attracted most attention have done so on account of their medical interest, most of them being pathogenic. Effort has therefore been directed towards obtaining a simple method of culturing the organisms rather than solving the fundamental problems of growth which are involved. As a consequence much of the work is disjointed and cannot be co‐ordinated in review (Section III).The growth factors of lower organisms, especially those which are essential, are obviously similar to the vitamins required by higher organisms. Advance of our knowledge of vitamins has led to multiplication of the number of factors that are known to be required by animals. In spite of this and the increased information now available, none of these vitamins has been definitely shown to be identical with any of the factors required by lower organisms, though frequently the resemblance has proved to be very close (Section IV).The question of production of growth factors by lower organisms involves (a) factors for higher organisms, and (b) factors for other lower organisms. It has been shown that production of both these types of growth factor is a widespread occurrence. A more difficult problem awaiting solution is mentioned, viz. the production of factors required for growth of a given species by that organism itself. This may occur in the case of yeasts, for example, which do not grow from a small seeding on a synthetic medium if bios is absent, though if a large seeding is used a sufficient crop may be obtained to show that bios is present therein (S

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1933.tb01086.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

Summary.I. In the last few years it has been found that:(a) A large proportion of the acid‐soluble phosphate originally classed as “inorganic” is actually combined with creatine (creatinephosphoric acid, phosphocreatine, phosphagen).(b) Most of the organic phosphate hydrolysed by the muscle enzymes during autolysis (the fraction hitherto known as “lactacidogen”) is adenosinetriphosphoric acid (adenylpyrophosphate).(c) There is no hexosediphosphoric ester in normal muscles, but a small amount of a hexosemonophosphoric ester. To this the name lactacidogen is now applied.2. Concerning the chemical events accompanying activity of a muscle, two discoveries in particular have greatly altered their interpretation:(a) It is found that the production of lactic acid occurs partly, and in some cases entirely, after the activity has ceased.(b) The production of lactic acid does not occur at all in muscles suitably poisoned with fluoride or iodoacetate. In such muscles the energy production is proportional to the extent of the accompanying phosphagen breakdown and is limited by the amount of phosphagen in reserve.3. Arising out of these and other considerations discussed in the text, a reasonable working hypothesis of muscular contraction is that the thermal and mechanical energy released in activity comes from the (exothermic) breakdown of phosphagen During the subsequent recovery period this phosphagen is resynthesised, the necessary energy being derived:(a) In the absence of oxygen; from the conversion of glycogen to lactic acid. Restitution in this case is only complete in muscles which have used up nearly all their reserve of phosphagen. There seems to be no alternative to the glycolysis mechanism as an anaerobic source of energy.(b) In the presence of oxygen, from the combustion probably of any available foodstuff, though carbohydrate seems to be the material used for choice by skeletal muscles.4. Other directions in which rapid advance has been made in recent years are:(a) The isolation of the constituent parts of the ferment system responsible for the glycolytic process in muscle.(b) The perfection of a delicate and rapid method of measuring the vapour pressure of muscles. One of the immediate results of the application of this technique has been the demonstration that the catabolic changes so far studied in connection with muscular activity do not account for all the osmotic pressure change. There must remain reactions of quite considerable extent so far und

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1933.tb01087.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

Summary.1. The creatine of vertebrate muscle is mainly present in the form of a compound with phosphoric acid.2. This labile compound is intimately associated with muscular contraction. It is broken down in activity and reconstituted during rest, and is a more immediate energy source than is glycolysis. It is also broken down under conditions which are unfavourable to the organism as a whole.3. Similar considerations appear to hold in the case of the electrical organs of certain fishes, and may possibly hold for ciliary motion also.4. The creatine of the vertebrates is replaced, in many if not in all invertebrates, by arginine, which also forms a labile compound with phosphoric acid, and this is of a physiological significance exactly parallel to that of creatine phosphoric acid.5. The preparation, properties, and physiological behaviour of these compounds are described and discussed, while the methods in common use for their estimation are also described.6. Guanidine derivatives other than creatine and arginine may also behave in the same way, giving phosphagenic compounds of similar functional importance. One such compound appears to be present in cephalopod muscle.7. Creatine phosphate is practically confined to the vertebrates, whereas arginine phosphate is never found in members of that phylum. Both compounds have been found together in an echinoid and in an enteropneust. The Echinoderm‐Enteropneust theory of vertebrate affinity, previously postulated on purely morphological grounds, seems thus to find new support on biochemical grounds.8. The Cephalopoda appear to contain a phosphagen whose base is not arginine, whereas arginine phosphate appears to be present in the Lamellibranchiata. This is possibly of evolutionary significance, since the Lamellibranchiata are believed to have branched off from the main line of evolution at a date considerably earlier than that of the divergence of the other Mollusca.9. Protozoa appear not to contain phosphagen, but with a possible exception in the case of the Coelenterata, the Metazoa all make use of some phosphagen compound.The author wishes to express his gratitude to Dr Joseph Needham and Mrs Needham for their continual help and advice, and to the Department of Scientific and Industrial Research for a grant, during the tenure of which this article was writte

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1933.tb01088.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY