bluuebunny/crossref_metadata_2025_split huggingface dataset:
SUR LA BIOCHIMIE COMPARÉE DES PHOSPHAGÈNES ET LEUR RÉPARTITION CHEZ LES ANIMAUX
Authors: THOAI NGUYEN VAN , ROCHE JEAN 
Published: January 2008

Résumé1. La répartition des phosphagènes, dérivés phosphoriques labiles qui servent à la reconstitution de l'acide adénosinetriphosphorique dépensé au cours de la contraction musculaire, a été pendant longtemps reliée á la phylogénie. Les phosphagènes actuelle‐ment connus: phosphocréatine, phosphoarginine, phosphoglycocyamine, phospho‐taurocyamine, phosphohypotaurocyamine, phospholombricine, phosphoophéline, présentent, en fait, une répartition très inégale. Les deux premiers sont les plus répandus, la phosphocréatine chez les Vertébrés et plusieurs groupes d'Invertébrés, la phosphoarginine chez la majorité des Invertébrés. Les cinq autres phosphagènes ne se rencontrent que chez les Annélides et les Sipunculiens.2. Si les sept phosphagènes offrent entre eux une grande parenté chimique, soit parce qu'ils dérivent les uns des autres, soit parce qu'ils présentent une grande similitude de structure, leur formation ne semble être liée ni avec l'habitat ni avec la phylogénie. L'étude de leur biogenèse et surtout des relations entre les différentes phosphoryltransférases constituent les nouvelles méthodes d'approche des problèmes posés par la diversité des phosphagènes.3. Les Oursins camarodontes et plusieurs Annélides sont caractérisés par la présence de doubles phosphagènes. L'association la plus communément rencontrée est constituée par les deux phosphagènes principaux: phosphocréatine et phosphoarginine, soit entre eux, soit entre l'un de ceux‐ci avec l'un ou l'autre des phosphagènes secondaires, phosphoglycocyamine, phosphotaurocyamine. La signification bio‐logique des doubles phosphagènes est discuée.Summary1. The distribution of phosphagens—labile phosphorus compounds which function in the regeneration of adenosine triphosphoric acid broken down in the course of muscular contraction—has for a long time been brought into relation with phylogeny.The seven phosphagens at present known show in point of fact an unequal distribution. Two of them are the most abundant: phosphocreatin in the vertebrates and several groups of invertebrates, phosphoarginine in the majority of the invertebrates. The five other phosphagens occur only in annelids and sipunculids.2. While the various phosphagens are closely related chemically, either by being derived the one from the other or by having a closely similar structure, their occurrence does not seem to be related either to habitat or to phylogeny. The study of their biogenesis and especially of the relation between the different phosphoryltransferases constitute the new modes of approach to the problems presented by the diversity of the phosphagens.3. The camarodont echinoids and several annelids are characterized by the presence of double phosphagens. The most usual association is that of the two principal phosphagens, phosphocreatin and phosphoarginin, either with one another, or one of them with one of the secondary phosphagens, phosphoglycocyamine and phospho‐taurocyamine. The biological significance of the double phosphagens is discussed.
THE ENZYMIC BASIS OF SPECIFIC ANTIBACTERIAL ACTION BY STRUCTURAL ANALOGUES
Authors: RICHMOND M. H. 
Published: January 2008

Summary1. The mechanism of action of structural analogues is examined to discover the extent to which their properties make them effective antibacterial agents in vivo.2. Two main types of structural analogue may be recognized. First, there is the type which competes with a natural metabolite for a recognition site on the surface of a protein. Secondly, there are a few examples–notably cycloserine, and possibly penicillin–which inhibit non‐competitively by reacting covalently with an enzyme to inhibit its action. In general, inhibitors which react covalently are more effective in vivo than those which inhibit competitively.3. Analogues which inhibit competitively act in three main ways: they may compete at the active centre of a single enzyme, or exert a ‘false feedback’ inhibition of the endogenous supply of an essential metabolite, or repress the formation of enzymes necessary for the biosynthesis of an essential metabolite.4. Although structural analogues which inhibit competitively in one of these three ways can cause temporary inhibition in the growth of bacterial cells, their bacteriocidal effect is low, since resistant bacterial populations readily emerge.5. Resistance to structural analogues which inhibit competitively at the active centre of a single enzyme may occur physiologically by the accumulation of the precursor to the inhibited enzyme.6. Resistance to structural analogues which inhibit competitively may also occur by mutation. In the case of analogues acting at the active centres of enzymes, mutation may lead to resistance by lowering the affinity of the relevant enzyme for the analogue. Resistance to structural analogues acting as ‘false feedback’ inhibitors occurs when a mutation causes the synthesis of an enzyme with a lowered affinity for the structural analogue as a feedback inhibitor. Similarly, organisms resistant to the action of analogues as repressors are probably the result of a mutation which lowers the affinity of the ‘genetic repressor’ for the analogue in its role as the ‘low molecular weight repressor’.7. Inhibitors which react covalently with an enzyme have certain advantages not found with analogues which act competitively, and these are discussed in relation to the mode of action of the cholinesterase inhibitor, di‐iso‐propylfluorophosphate. One advantage of this type of inhibitor is that reversal by the normal enzyme substrate does not readily occur. Secondly, this type of inhibitor is active at appreciably lower concentrations than simple competitive inhibitors.8. The antibacterial action of cycloserine and penicillin are examined to see to what extent they are examples of structural analogues which react covalently with essential enzymes.9. The fact that analogues which react covalently with enzymes are more effective inhibitors than analogues which act competitively, suggests that some form of covalent reaction may often be involved in the action of antibiotic substances.
CHEMICAL EMBRYOLOGY OF THE CRUSTACEA
Authors: GREEN J. 
Published: January 2008

Summary1. The dry weight of a neonate crustacean is sometimes lower than the initial dry weight of the egg, owing to utilization of respiratory substrates, as in Daphnia, where the dry weight decreases by 16–25 %. In Artemia any loss is compensated by an uptake of salts so that there is no change in dry weight during the course of embryonic development. The embryos of Ligia receive nutrients secreted into the maternal brood pouch, and the dry weight of the neonate is greater than the initial dry weight of the egg.2. Early embryos of Simocephalus, Artemia and Balanus consume less oxygen per unit dry weight than older embryos. The increase in oxygen consumption from early to late embryos is approximately six to eightfold.3. Oxygen consumption decreases when the rate of embryonic development of Artemia is reduced by increasing osmotic pressures in the external medium.4. Glycogen is formed rather than utilized in the embryos of Simocephalus and Artemia. In the latter the main carbohydrate reserve is trehalose, which is transformed to glycogen and glycerol. The relative formation of these two substances is influenced by external osmotic pressures. At high external osmotic pressures more glycerol is formed, and this aids osmotic rupture of the tough outer shell of the egg.5. Trehalose seems to be important in relation to the dormant state of Artemia embryos. The embryos which develop rapidly in the maternal brood pouch contain much less trehalose than those which become encysted and dormant.6. The proportion of the initial lipid content of a crustacean egg that is utilized during development is very variable. In Homarus 60% disappears by time the neonate emerges, in Ligia 32%, and in Artemia the decrease is very slight, or there may even be a slight increase.7. Haemoglobin in the eggs of Cladocera does not appear to act as a respiratory pigment, but does serve to accelerate development in poorly aerated water. It is suggested that the main function is to act as a supply of stable protein.8. The haemochromogen found in the gut of late embryos of Daphnia appears to be formed in part at least from haemoglobin, which diminishes in concentration as development proceeds.9. Breakdown of haemoglobin during embryonic development of Daphnia is not accompanied by formation of bile pigments.10. Biliverdin is synthesized in the embryonic eyes of Polyphemus but not elsewhere in the embryo.11. The carotenoproteins in the eggs of many different crustaceans break down towards the end of embryonic development, liberating free carotenoid. It is suggested that these proteins are stabilized and held in reserve by linkage to a carotenoid until a particular stage of embryonic development has been reached.12. Metabolic pathways in the formation of astaxanthin from β‐carotene may involve monoketo and diketo carotenes, or by an alternative route monohydroxy and dihydroxy carotenes.
CAROTENOPROTEINS IN INVERTEBRATES
Authors: CHEESMAN D. F. , LEE W. L. , ZAGALSKY P. F. 
Published: January 2008

SUMMARYTrue carotenoproteins are defined as complexes in which a carotenoid and a protein are in stoichiometric combination. Very few carotenoproteins have been purified, but their presence in extracts may often be presumed from spectroscopic evidence. Carotenoids have been found in stoichiometric association with simple proteins, lipoproteins and glycoproteins. Many lipoproteins also occur in which carotenoids form part of the lipid prosthetic group. Although the relationship between the carotenoid and the remainder of the complex may in these cases not appear to be stoichiometric, it often shows some evidence of selectivity.Carotenoproteins are widely distributed among the invertebrate phyla. They are found mainly in exoskeleton or ectoderm and in eggs and ovaries. Their isolation by standard techniques of protein chemistry is facilitated by their characteristic spectral properties.The ease with which carotenoid prosthetic groups are removed from apoproteins suggests that covalent linkages are not involved in the complex formation. The union of carotenoid with apoprotein has been shown, in at least two cases, to stabilize the carotenoid against photo‐oxidation and the protein against denaturative changes of tertiary structure. In crustacyanin, the carapace pigment of the lobster, there is clear evidence that the carotenoid is responsible for establishing the very complex quaternary structure.Only astaxanthin, astaxanthin esters and canthaxanthin have been unequivocally identified as carotenoid prosthetic groups of true carotenoproteins. Experiments in the specificity of interaction of a series of carotenoids with the apoprotein of crustacyanin have indicated the requirement of one or both of the 4‐ and 4′‐keto groups of the carotenoid for interaction with the protein.It is suggested that, at least in this case, the carotenoid‐protein interaction might occur between carotenoid keto groups and basic residues of the protein in such a way as to provide a lock on the tertiary configuration.Carotenoproteins may participate in a variety of functions including protective coloration, photosensitivity, electron transport and enzymic activity. They appear, furthermore, to play some part in development.
BIOCHEMICAL STUDIES ON THE PRODUCTION OF MARINE ZOOPLANKTON
Authors: CORNER E. D. S. , COWEY C. B. 
Published: January 2008

Summary1. Phytoplanktonic algae vary in their value as food for zooplankton and no single algal food can meet the full nutritional needs of zooplanktonic animals. Perhaps this is because optimal amounts of essential micronutrients are not all present in any one alga. The dietary requirements of planktonic Crustacea, as far as they are known, bear some resemblance to those of vertebrates.2. The proteins of phytoplankton are similar in amino acid composition to those of zooplankton. This circumstance should favour efficient synthesis of protein by the animal, for assuming amino acids are all released in the gut and absorbed at approximately the same rate, they will be presented to the tissues in roughly the right relative amounts for protein formation.3. Zooplankton are able to alter the characteristics of the fatty acids present in their diet by elongating the carbon chain length and by increasing the degree of unsaturation.4. Measurements of phosphorus and nitrogen excretion indicate that zooplankton are metabolically very active. Some of the very high rates of phosphorus excretion are questioned and it is suggested that some portion of the phosphorus compounds liberated by zooplankton have passed straight through the gut without being assimilated. It is unlikely that all forms of organically bound phosphorus are equally rapidly assimilated and turned over by zooplankton.5. Estimates of the rate of ammonia excretion by zooplankton differ markedly. This may be a matter of size/surface area of the animals concerned—smaller animals excreting more rapidly than larger animals. It has been claimed that a‐amino nitrogen is released in considerable quantities by zooplankton but the evidence is not yet compelling.6. There is considerable disagreement on the efficiency of food assimilation and conversion by zooplankton. One view is that irrespective of the quantity of phyto‐plankton ingested assimilation is uniformly high. The opposing view holds that when rapid ingestion of phytoplankton occurs the percentage assimilated falls. More information on the feeding behaviour of zooplankton and on the physiology of their digestive processes is required before this controversy can be satisfactorily resolved.
SELECTION and QUANTITATIVE CHARACTERS IN FIELD CROPS
Authors: WALKER J. T. 
Published: January 2008

Summary1. It is vital that there should be no decrease in the rate of improvement of crop plants. In drafting the background to the inheritance of quantitative characters it is suggested that greater understanding of genetic mechanisms is needed rather than further increase in biometrical complexity. Selection is a very powerful force; it could be used to conserve genetic variation whilst effecting useful change.2. Various breeding techniques, examined in a framework of directional, stabilizing and disruptive selection, are found to be tied to certain crops. Breeders of self‐fertilizing plants handle quantitative variation differently from those working with outbreeders.3. Physiological analysis and partitioning of characters have not in themselves made large contributions to solving problems caused by complex traits, but both have been informative in conjunction with biometrical studies. In some circumstances more use could profitably be made of selection indices.4. Heterozygote advantage and genetic balance play major parts in stabilizing selection. Modal selection can sometimes lead to increased fitness, conforming with the concept of genetic homeostasis.5. Disruptive selection has apparently operated during the evolution of crop plants. To be beneficial to breeders it should be multidirectional; intercrossing of peripheral lines might then form ‘springboard’ populations allowing further advance from selection plateaux.6. As the boundaries of cultivation are extended so the need will increase for plant populations with inherent stability of performance. Few crops are yet amenable to the production of F1 hybrid seed, so polygenes should be manipulated to form balanced, heterozygous adaptive complexes. Systems of selection must be refined to deal effectively with the heterogeneous populations from which such complexes are likely to arise.7. Studies on composite crosses and related projects tie in well with other work on selective forces in adaptation. New allopolyploids offer hope in some plant groups, but induced mutation is of restricted value.8. Cryptic variation and selection can be important in many breeding methods, and should be considered when dealing with quantitative aspects.9. Changes in locality can reveal startling amounts of unsuspected variability: such ‘environmental segregation’ could be harnessed, for example, by alternation of selection centres when breeding for general adaptability.10. Persistence of variation, which may occur through selection favouring hetero‐zygotes despite strict inbreeding, is also considered in terms of heterozygous gene complexes. Tightness of linkage is the key to the durability and behaviour of super‐genes, and analysis of the simpler ones could lead to better understanding of the vastly complicated systems controlling fitness and productivity.
PASSIVE IMMUNITY AND ITS TWSFER WITH SPECIAL REFERENCE TO THE HORSE
Authors: JEFFCOTT L. B. 
Published: January 2008

Summary1. There are relatively few references in the literature on the transfer of passive immunity to the newly born foal. Transmission of immunity has been established as being post‐natal in origin. At birth the serum is apparently agammaglobulinaemic and only trace levels of antibody are detectable. Peak levels of immunity are reached a few hours after ingestion of colostrum.2. Immune proteins derived from the dam's serum are selectively concentrated in the mammary gland before parturition. In the horse the predominant immuno‐globulins of colostrum are IgG and IgG(T).3. The mechanism of absorption of colostral proteins by the newborn animal is complex and there are considerable species differences. In newly born ungulates the uptake is effected into specialized epithelial cells of the small intestine by pinocytosis. This is followed by transfer of the proteins across the cell, their extrusion into the lamina propria and into the lymphatics before they reach the systemic circulation.4. The absorption of macromolecules occurs without degradation in neonatal ungulates, is non‐selective and can be enhanced by solvent factors in the colostrum. The duration of transfer is influenced by stress and the administration of adrenal corticoids.5. The period of absorption in ungulates is short (< 48 hr.) compared to that in rats and mice (13–21 days). In the foal the small intestine is permeable to macro‐molecules for less than 24 hr. after birth.6. After birth there is a gradual decline in the concentration of protective antibody to insignificant levels by 5–6 months. The foal shows evidence of active immunity from one to 3 months of age.7. A transient proteinuria is detectable in newly born animals fed colostrum soon after birth. This proteinuria occurred in two phases, initially there were rising levels of urinary protein followed by sharply declining levels to 36 hr. of life. Feeding high protein colostrum during and after the time of intestinal closure did not prolong the period of proteinuria. The constituents of the proteinuria were almost exclusively low molecular weight proteins of milk of colostral origin, β‐lactoglobulin and α‐lact‐albumin.8. The importance of neonatal infections in the foal has been well documented but there are few accounts of its relation to passive immunity.9. A natural immunological incompatibility, haemolytic disease, occurs in the horse. The disease can be diagnosed in the mare in late pregnancy and prevented in the foal by completely withholding the dam's colostrum for 24 hr. of life.
OBLIGATE PARASITISM BY PHYTOPATHOGENIC FUNGI
Authors: SCOTT K. J. 
Published: January 2008

Summary1. This review is concerned with the obligate parasitism of the downy mildew, powdery mildew and rust fungi.2. Mechanisms which determine resistance and susceptibility are incompletely understood. The three possibilities so far advanced, namely, hypersensitivity, phyto‐alexins and nutrition are all inadequate to explain specificity. It is postulated that compounds carrying specificity are released by the invading pathogens and the interaction of the compounds with specific sites in the host cell determines whether a successful relationship is established. This hypothesis is based on the observation that host and pathogen protoplasts do not come in direct contact with each other and cells removed from the invading pathogen are affected. It should be possible to investigate this question now that some rust fungi have been cultured axenically.3. Invasion of host tissue by these pathogens leads to alteration in host metabolism. Respiration rates and the activity of the pentose phosphate pathway are enhanced. Possible mechanisms for the reoxidation of NADPH by molecular oxygen are discussed. In the later stages of infection, photosynthetic activity is decreased and this decrease is coupled to the enhanced activity of the pentose phosphate pathway through NADPH availability.It is still not clear whether photosynthetic activity is increased or decreased during the early stages of infection. Nutrients from other parts of the plant accumulate at sites of infection, resulting in retarded growth of the host. Possible roles of hormones in nutrient mobilization and ‘green island’ formation are discussed.Changes in intermediary metabolism can be correlated with changes in amounts of nucleic acids in infected host cells. Chloroplast polysomes and ribosomes decrease during the early stages of infection but cytoplasmic ribosomes increase during patho‐genesis. This increase more than compensates for the decrease in chloroplast ribosomes resulting in an overall increase in cellular RNA.4. Some members of the Pucciniaceae and one member of the family Melamp‐soraceae have now been cultured axenically. Nutritional studies indicate that these fungi are relatively non‐specific with respect to their carbohydrate and amino‐acid nitrogen sources but do have a specific requirement for either cysteine, methionine or homocysteine. Essential metabolites such as cysteine and cysteine‐containing peptides move from hyphae into the medium and these may be important in amino‐acid transport.Two stages in the development of axenic rust cultures are still imperfectly understood ‐ the transition from germ tube to saprophytic mycelium and the fate of the colonies once formed. Further knowledge of the factors which control these stages may well suggest approaches to the axenic culture of other groups of obligately parasitic fungi.