L'action du chlorure de lithium et du sulfocyanure de sodium sur la viscosité de la nucléohistone et des extraits d'embryons d'Amphibiens

Summary (1) LiCl increases the viscosity and decreases the rigidity of nucleohistone; NaSCN has opposite effects.(2) The effects of LiCl and NaSCN on the viscosity of amphibian embryo extracts, as observed byRanzi and his coworkers, seem to be due to the action of these salts on nucleohistone.     

Action du LiCl sur de jeunes blastodermes de poulet cultivésin vitro

Summary The young blastoderms cultivatedin vitro, by the method ofNew, slightly modified, grow abnormally on a medium of albumen mixed with LiCl solution. It acts in the first place upon the morphogenesis, secondarily upon the differentiation of organs, if they are able to develop.

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Travail subventionné par le Fonds national suisse de la Recherche scientifique.     

Kinetics and Na-dependence of riboflavin absorption by intestine in vivo

Conclusion The transport of riboflavin across the intestinal mucosa is certainly not by a system of passive diffusion. It necessitates the presence of a specific transporter in the membrane, thus explaining saturation kinetics noted. The transport is dependent on the presence of Na⁺ in the perfusion medium. However, it is not as yet possible to say whether transport is against an electrochemical gradient or a system of facilitated diffusion with simple equilibrium of concentrations extra-and intra-cellular.

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Résumé L'absorption intestinale de la riboflavine est mesurée in vivo par perfusion d'un segment proximal du jéjunum chez le rat. Le transport de la vitamine à travers la muqueuse intestinale suit une cinétique de saturation (K _t =3M; V _max =0,26 nMole par min et par g de tissu frais). Il est fortement réduit (de 40 à 50%) lorsqu'on substitue au NaCl isotonique du milieu de perfusion du mannitol ou du LiCl isotoniques.

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Acknowledgements. We should like to thank Prof.B. Blanc who made possible the completion of this work, Prof.W. Wilbrandt and Prof.G. Semenza for their advice and criticism. The work was supported by the Foundation pour la Recherche Nutritionelle (financed by Zyma S. Y., Nyon and Union Laitière Vaudoise, Lausanne).     

Diketopiperazines containing L-proline from Streptomyces lavendulae and their stereochemistry in solution

Summary l-Valyl-l-proline (I),l-leucyl-l-proline (II),l-phenylalanyl-l-proline (III) andl-isoleucyl-l-proline (IV) anhydrides were isolated from the cultures ofStreptomyces lavendulae No. 314 and, on the basis of¹³C-NMR and CD spectra, their stereochemistry in solution is described.Acknowledgments. The authors would like to express their sincere thanks to Prof. H. Ogura, Kitasato University, for kind supply of the authenticl-valyl-l-proline anhydride and to Mr. A. Takakuwa, JASCO, for measuring the CD curves with J-40 automatic recording spectropolarimeter.     

Geometrical constructions equivalent to non-linear algebraic transformations of the plane in Newton's early papers

Summary The theory of constructive formation of plane algebraic curves in Newton's writings is discussed in § 1: the apparatus by which Newton forms the curves, Newton's theorems on forming unicursal curves, his theory of conics, and his theory of (m, n) correspondence. Special Cremona plane and space transformations obtained by Newton's organic method are dealt with in § 2. The article ends with § 3, which shows two different directions in the theory of the constructive formation of plane algebraic curves in the XVIII-XIXth centuries. A synopsis is appended.Abbreviations MPN The Mathematical Papers of Isaac Newton, edited by D. T. Whiteside, Vols. 1–3, Cambridge, 1967–1969 - Hudson H. Hudson, Cremona Transformations in Plane and Space, Cambridge, 1927 - PT (abridged) Philosophical Transactions of the Royal Society 1665–1800 (abridged), London, 1809 - Andreev ₁ K. A. Andreev, On geometrical correspondences ... (in Russian), Moscow, 1879 - Andreev ₂ K. A. Andreev, On the Geometrical Formation of Plane Curves (in Russian), Kharkov, 1875     

Über den Einbau von Dipeptiden in Ergotoxin-Alkaloide

Summary l-Valyl-l-leucine-U-¹⁴C,l-valyl-l-proline-U-¹⁴C-lactam andl-leucyl-l-proline-U-¹⁴C-lactam were administered to submerged cultures of an ergotoxine-mixture-producing strain ofClaviceps purpurea. The added dipeptides were split by the fungus into the corresponding amino acids prior to incorporation. Apparently dipeptides are no immediate precursors for the peptide side-chain of ergotoxinealkaloids.     

Further studies on polyacrylamide gel electrophoresis of water-soluble proteolipid-protein from bovine brain white matter

Zusammenfassung Wasserlösliche, proteolipide Proteine wurden von der weissen Hirnsubstanz durch Isolierungsmethoden vonTenenbaum undFolch ² gewonnen. Ohne Lyophilisation ergab die Disk-Elektrophorese bei pH 8.3 zwei Banden.

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The authors express their appreciation to Dr.K. Ueki, Dr.Y. Takahashi, Dr.Y. Takemoto and Dr.T. Kotoku.     

Interaction between sugars and amino acids in intestinal absorption by rat,in vivo

Summary The inhibitory action ofl-leucine on the intestinal absorption ofd-glucose andd-galactose, as well as the inhibitory action ofd-galactose on the absorption ofl-leucine at various concentrations by rat small intestine has been studied. The further effect was more clearly evidenced when the medium was perfunded through the intestine in a closed circuit system using a peristaltic pump.     

Catalytic properties of synthetic pentapeptides

Zusammenfassung Es wurde das Pentapeptidl-Thr-l-Ala-l-Abu-l-His-l-Asp synthetisiert, seine katalytische-hydrolytische Wirkung auf Essigsäure-p-nitrophenylester geprÜft und die katalytische Aktivität ca. 1/3 derjenigen seines isosterenl-Thr-l-Ala-l-Cys-l-His-l-Asp festgestellt.

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Work done on a leave of absence from the Research Council of Alberta, Canada.     

Eco-physiological studies onZornia diphylla pers. with reference to adaptive seed dormancy

Summary Seeds ofZornia diphylla possess a complex type of dormancy which is of great survival value for the species. Seeds show polymorphism. The optimum temperature for germination explains the cause of its distribution in the tropics. The grazing and scraping promotes the vegetative growth.The author is grateful to Dr.R. Sahai and Dr.R. S. Tripathi, Gorakhpur University, for guidance and to Dr.Y. B. Singh, Principal, and Dr.G. C. Srivastava, Head Dept. Botany, for encouragement and facilities. Thanks are due to my colleagues late SriP. N. Gupta, SriJ. Abraham, SriF. Abbasi, and Dr.A. B. Sinha for their cooperation.     

Effets d'analogues du chloramphénicol sur la différenciation de l'∄uf de l'oursinParacentrotus lividus

Summary The effects ofl-threo-chloramphenicol and thiophenicol on the differentiation of sea-urchin eggs are compared with those exerted byd-threo-chloramphenicol. Onlyd-threo-chloramphenicol caused vegetalization;l-threo-chloramphenicol inhibited development. These effects resemble those of nitrobenzene. Thiophenicol, differing fromd-threo-chloramphenicol by replacing the nitro group with a methylsulphonyl group, slows down development at high concentrations. The effects of chloramphenicol on oxidative phosphorylation and synthesis of proteins are discussed. It is suggested that both the steric configuration typed-threo of the side chain and the presence of a nitro group are necessary for the vegetalizing activity.     

Learned aversion and rearing movement in rats given LiCl,PbCl2 or NaCl

Summary The effects of an i.p. injection of 0.15 M LiCl resembled closely the effects of another toxic substance, 0.005 M PbCl₂, on conditioned aversion to saccharin and rearing movements in male rats. The findings suggest that nonspecific aversive after-effects of a LiCl injection can account fully for prompt effects of LiCl on rearing behavior.Acknowledgments. I thank Elin Kristensen and Christian Hoffmann for testing the rats, Klaus Thomsen and Ole Olesen for constructive criticism and P. Carl Petersens Fund, Aarhus University and the Danish Medical Research Council for financial support.     

Newton and the classical theory of probability

Summary Probabilistic ideas and methods from Newton's writings are discussed in § 1: Newton's ideas pertaining to the definition of probability, his probabilistic method in chronology, his probabilistic ideas and method in the theory of errors and his probabilistic reasonings on the system of the world. Newton's predecessors and his influence upon subsequent scholars are dealt with in §2: beginning with his predecessors the discussion continues with his contemporaries Arbuthnot and De Moiver, then Bentley. The section ends with Laplace, whose determinism is seen as a development of the Newtonian determinism.An addendum is devoted to Lambert's reasoning on randomness and to the influence of Darwin on statistics. A synopsis is attached at the end of the article.Abbreviations PT abridged Philosophical Transactions of the Royal Society 1665–1800 abridged. London, 1809 - Todhunter I. Todhunter, History of the mathematical theory of probability, Cambridge, 1865 To the memory of my mother, Sophia Sheynin (1900–1970)     

Evaluations of the beta probability integral by bayes and price

Summary The contribution of Bayes to statistical inference has been much discussed, whereas his evaluations of the beta probability integral have received little attention, and Price's improvements of these results have never been analysed in detail. It is the purpose of the present paper to redress this state of affairs and to show that the Bayes-Price approximation to the two-sided beta probability integral is considerably better than the normal approximation, which became popular under the influence of Laplace, although it had been stated by Price.The Bayes-Price results are obtained by approximating the skew beta density by a symmetric beta density times a factor tending to unity for n , the two functions having the same maximum and the same points of inflection. Since the symmetric beta density converges to the normal density, all the results of Laplace based on the normal distribution can be obtained as simple limits of the results of Bayes and Price. This fact was not observed either by Laplace or by Todhunter.     

Emerging knowledge of regulatory roles of <Emphasis Type="SmallCaps">d-</Emphasis>amino acids in bacteria

The d-enantiomers of amino acids have been thought to have relatively minor functions in biological processes. While l-amino acids clearly predominate in nature, d-amino acids are sometimes found in proteins that are not synthesized by ribosomes, and d-Ala and d-Glu are routinely found in the peptidoglycan cell wall of bacteria. Here, we review recent findings showing that d-amino acids have previously unappreciated regulatory roles in the bacterial kingdom. Many diverse bacterial phyla synthesize and release d-amino acids, including d-Met and d-Leu, which were not previously known to be made. These noncanonical d-amino acids regulate cell wall remodeling in stationary phase and cause biofilm dispersal in aging bacterial communities. Elucidating the mechanisms by which d-amino acids govern cell wall remodeling and biofilm disassembly will undoubtedly reveal new paradigms for understanding how extracytoplasmic processes are regulated as well as lead to development of novel therapeutics.     

Newton's early computational method for dynamics

On December 13, 1679Newton sent a letter toHooke on orbital motion for central forces, which contains a drawing showing an orbit for a constant value of the force. This letter is of great importance, because it reveals the state ofNewton's development of dynamics at that time. Since the first publication of this letter in 1929,Newton's method of constructing this orbit has remained a puzzle particularly because he apparently made a considerable error in the angle between successive apogees of this orbit. In fact, it is shown here thatNewton's implicitcomputation of this orbit is quite good, and that the error in the angle is due mainly toan error of drawing in joining two segments of the oribit, whichNewton related by areflection symmetry. In addition, in the letterNewton describes quite correctly the geometrical nature of orbits under the action of central forces (accelerations) which increase with decreasing distance from the center. An iterative computational method to evaluate orbits for central forces is described, which is based onNewton's mathematical development of the concept of curvature started in 1664. This method accounts very well for the orbit obtained byNewton for a constant central force, and it gives convergent results even for forces which diverge at the center, which are discussed correctly inNewton's letterwithout usingKepler's law of areas.Newton found the relation of this law to general central forces only after his correspondence withHooke. The curvature method leads to an equation of motion whichNewton could have solvedanalytically to find that motion on a conic section with a radial force directed towards a focus implies an inverse square force, and that motion on a logarithmic spiral implies an inverse cube force.     

Synthesis of L-4-amino-3-isoxazolidinone,the unnatural stereoisomer of cycloserine and its antibiotic activity

Zusammenfassung Eine direkte Synthese vonl- undd-Cycloserin ausl- undd-Serin wurde beschrieben. Die bakteriostatischen Effekte der drei Formen von Cycloserin (d-,l-unddl-) aufE. coli in synthetischem Medium wurden verglichen.     

J. Zaragosa's centrum minimum,an early version of barycentric geometry

Summary Using the properties of the Centre of Gravity to obtain geometrical results goes back to Archimedes, but the idea of associating weights to points in calculating ratios was introduced by Giovanni Ceva in De lineis rectis se invicem secantibus: statica constructio (Milan, 1678). Four years prior to the publication of Ceva's work, however, another publication, entitled Geometria Magna in Minimis (Toledo, 1674), 2 appeared stating a method similar to Ceva's, but using isomorphic procedures of a geometric nature. The author was a Spanish Jesuit by the name of Joseph Zaragoza.Endeavouring to demonstrate an Apollonius' geometrical locus, Zaragoza conceived his idea of centrum minimum — a point strictly defined in traditional geometrical terms — the properties of which are characteristic of the Centre of Gravity. From this new concept, Zaragoza developed a theory that can be considered an early draft of the barycentric theory that F. Mobius was to establish 150 years later in Der barycentrische Calcul (Leipzig, 1827).Now then, whereas Ceva's work was rediscovered and due credit was given him, to this day Zaragoza's work has remained virtually unnoticed.     

A probabilistic “New Principle” of the 19th century

We discuss the evolution of an idea which contains, within the setting of an urn model, the notion of a martingale. The idea is to be found inPoisson (1837) but its main proponent isCatalan in a series of papers beginning in 1841, in partial ignorance ofPoisson's work. The usualBayesian coloration is present. A letter fromBienaymé of 1878, possibly his last, toCatalan elucidates the origin of the idea, and illustrates the personal relations of French probabilists at the time.