Photochemistry of riboflavin

Résumé Le spectre d'absorption, les caractéristiques luminescentes et photochimiques de la riboflavine sont présentés. L'interprétation des données expérimentales d'autres auteurs sur la décomposition photochimique de l'eau sensibilisée par la riboflavine est critiquée. Il faut distinguer deux cas: dans les réactions photochimiques qui ont lieu en l'absence de donneurs d'électrons ajoutés, la portion ribosique de la riboflavine se comporte en donneuse d'électrons et elle est détruité. Par contre, en présence de donneurs d'électrons adjoutés, la riboflavine agit comme véritable photosensibilisateur et n'est pas consumée dans l'ensemble de la réaction photochimique.     

Effect of riboflavin and nicotinic acid on fat formation byPenicillium lilacinum thom

Résumé L'addition de riboflavine ou d'acide nicotinique aux cultures dePenicillium lilacinum Thom. a augmenté remarquablement la valeur iodique de la graisse formée. Mais c'est seulement la riboflavine, qui a accéléré la formation de la graisse.     

Hypervitaminosis in an insect larva

Résumé La biotine et la riboflavine, fortement concentrées, administrés à la larve de la phalène du riz,Corcyra cephalonica, sont toxiques. Les hautes concentrations de l'acide nicotinique n'ont des effets défavorables que sur la croissance des plus jeunes larves de l'insecte.     

Studies on relationships between riboflavin and folate

Résumé Des rats carencés en riboflavine, comparés aux contrôles, ont présenté une remarquable augmentation de la quantité de FIGlu éliminé. Une augmentation moins évidente a été observée dans l'élimination de AIC. Aucune variation, au contraire, en ce qui concerne les enzymes FIGlu transferase et AICR trànsformylase.     

Hydrolysis of riboflavin by plants

Résumé Il a été prouvé que l'hydrolyse de la riboflavine à l'aide d'une enzyme se produit dans les extraits de plantes appartenant aux familles desLiliacées, Amaryllidacées etCannas (ou Balisier).On a trouvé le lumichrome et le ribitole parmi les produits de l'hydrolyse. La réaction est stchiométrique, les conditions favorisant une activité optimale sont les suivantes: pH 7.4, température 37°, quantités catalytiques de glutathione reduit.     

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).     

Evidence for the metabolism of phospholipids and triacylglycerols in humanAscaris lumbricoides

Summary HumanAscaris lumbricoides has the necessary mechanism for the biosynthesis and degradation of phospholipids and triacylglycerols, as in most other species. Piperazine decreases the level of triacylglycerols of this parasite by stimulating the activity of lipase and partially inhibiting the activity of phosphatidate phosphatase.Acknowledgments. Thanks are due to the University of Kerala for facilities provided, Dr T. Ramasarma of the I.I. Sc., Bangalore for help in the labelling studies, Dr. G. D. Cain of the University of Iowa for valuable comments and Dr P. Vijayagopal of ANU for the gift of CDP-choline.     

Protein content of various developmental stages of three strains of the pink bollworm,Pectinophora gossypiella

Summary Comparison of the total body protein of male and female larvae, pupae, and adults of a diapause and 2 nondiapause strains of the pink bollwormPectinophora gossypiella indicated that the protein content of larvae of the diapause strains was significantly higher than of the non-diapause strain.I thank Drs D.R. Nelson and R.A. Bell of the U.S.D.A. Metabolism and Radiation Research Laboratory, Fargo, for facilities and guidance.     

Cerebellar decussation of fibres from the nucleus reticularis tegmenti pontis in the brain of the albino rat

Summary The existence of a cerebellar decussation of fibres from the medial portion of each nucleus reticularis tegmenti pontis (Rtp) of the albino rat is indicated. Definite cell loss in the medial aspect, of the most rostral third of Rtp is detectable after cerebellar hemisection involving parts or the entire depth of sublobule VIb. Cell loss in the medial aspect of the caudal half of Rtp is evident as a consequence of experimental lesions which damage both sublobules IIb and III.This work was supported by the Medical Research Council of New Zealand.Acknowledgments. A. special acknowledgment to. Mrs Heather Reid for her excellent preparation of the histological specimens. Grateful thanks to Mrs Maureen Owen for her careful typing assistance.     

Transparency in organisms

Summary The occurrence in animal phyla of species having a relatively transparent body is noted and measurements of the transmittance of medusae made in a spectrophotometer are reported, but the approximate nature of the results obtained with a commercial instrument and the importance of the correct physical design of the measuring apparatus are emphasized. The application to invertebrates of the structural explanation of the predominant transmission of incident light by the vertebrate cornea is discussed and the role of other factors considered. Destructive interference of the scattered rays, sufficient to account for the transparency of the cornea, has been shown not to demand a completely regular arrangement of collagen fibres. The small diameter and regularity of the fibrillar components in the muscles ofSagitta may be adequate to account for their transparency.I am grateful to Dr.D. M. Maurice for the encouragement of this interest, to Dr.E. G. Jordan for electron micrographs ofSagitta and to Mr.G. Ross (Department of Physics, Queen Elizabeth College) for helpful and critical discussion.     

Origin of the differences of superficial potentials in Rana esculenta]

The spatial distributions of superficial D.C. potentials on the skin of Rana esculenta have been compared to those of the intensity of short-circuit current (S.C.C.) expressing the transcutaneous active transport of sodium ions. It has been observed that the sites of maximum D.C. potentials coincide with the localisations of maximum S.C.C. values. Moreover, superficial D.C. potentials and S.C.C. are similarly modified by the depression of metabolic activity due to lowered temperature or poisoning by dinitrophenol (DNP). It is thus proposed that the spatial distribution of the transcutaneous active transport system for sodium ions is the origin of the electric generator of superficial D.C. potentials.     

Iron-sulfur proteins: Recent developments in the field

Summary Iron-sulfur clusters in proteins are now recognized as among the main types of electron-transferring groups in biological systems, besides heme and flavins. Recent developments have brought forth a better understanding about the ways the protein environment modulates the potential of the cluster by placing the cluster in a more or less hydrophobic surrounding. Refinement in models, extensive studies on the kinetics of electron transfer (e.g. by measurement of the electronic spin lattice relaxation time) and the introduction of novel spectroscopic methods (EXAFS, magnetic CD and others) in the elucidation of structures in various systems are among the main developments. Other advances include EPR studies of the spatial orientation of Fe−S centers in complex membraneous systems (e.g. in mitochondria) and the recent elucidation of the nature of center X in photosystem I by M?ssbauer-spectroscopy. M?ssbauer studies have also been described on a number of Fe−S proteins (nitrogenase, aconitase, some ferredoxins, etc.) and revealed the existence of novel structures that enlarged the number of known basic units of Fe−S centers. These advances include: 1. the discovery of a novel non-heme Fe-protein (called desulforedoxin) of the rebredoxin type, 2. the elucidation of the nitrogenase Fe−S centers and the nitrogenase cofactor and 3. the discovery of a three-iron cluster in several enzymes and some ferredoxins. The latter 3-Fe cluster seems capable of being converted into a classical 4-Fe cluster under appropriate conditions, a phenomenon that plays a role in activation-deactivation of some enzymes (e.g. aconitase). It is now recognized that some iron-sulfur clusters may be involved in systems devoided of any oxydation-reduction reaction and may act as sensors of the surrounding redox potential, triggering the activation/deactivation of an enzyme (cf. e.g. aconitase).     

Age-related response of citrate synthase to hydrocortisone in the liver and brain of male rats

Summary The activity of citrate synthase of the liver and brain of rats shows a gradual increase as a function of age. Adrenalectomy causes no significant change in the activity of citrate synthase in either of these tissues in young, adult or old rats. Administration of hydrocortisone to adrenalectomized rats depresses the activity of this enzyme maximally in the liver and brain of young rats. Administration of actinomycin D tends to normalize, the depressed level of this enzyme.Acknowledgments. The authors are indebted to Professor M.S. Kanungo of the Department of Zoology of Banaras Hindu University for helpful advice and facilities. A part of this project was presented at the 12th International Congress of Biochemistry, Australia, 1982.     

The quantification and differentiation of the drug receptor theory, c. 1910-1960

While historians have dealt with the origins of the concept of drug receptors in the work of Paul Ehrlich (1854-1915) and John N. Langley (1852-1925) as well as with some of its applications in modern pharmaceutical research, the history of the receptor theory as such has been neglected. Discussing major developments and conceptual changes in receptor theory between about 1910 and 1960 (including relevant contributions by A. V. Hill, A. J. Clark, J. H. Gaddum, E. J. Ari?ns and others), this paper attempts to fill this gap in historiography. It provides a case study of the unfolding of research under a new paradigm, but it considers also contemporary criticism and scepticism. By the early 1960s, quantitative investigations of drug action and interpretations of the experimental findings in terms of the receptor concept had become constitutive of the emerging field of 'molecular pharmacology'. Even then, however, receptors were still hypothetical entities.     

Induction of microsomal drug-metabolizing enzymes caused by hexobarbital

Summary Hexobarbital was given to anaesthetized mice for a period of 7 h by repeated i. p. injection, first of 100 mg/ kg, then several times of 50 mg/kg. A high level of hexobarbital was maintained in the liver. The activity of microsomal drug-metabolizing enzymes was induced by this treatment with hexobarbital. 30 min after a single i. p. injection of 100 mg/kg of hexobarbital, there was a significant inhibition of aminopyrine N-demethylase but none of cytochrome c and neotetrazolium reductases.—Hexobarbital in vitro inhibits aminopyrine N-demethylase but not cytochrome c reductase.     

Sterilization by irradiation of Cadra coutella (Wlk.) (Lepidoptera, Pyralidae) males increased by female sex pheromone

Sterilization by irradiation was studied in 0-24 hour old males of Cadra cautella (Ephestia cautella) exposed to 40 Krad of gamma radiation from a 60 cobalt source at a rate of 2250-2200 rad/minute in the presence of female sex pheromone. This radiation dose failed to induce the desired degree of sterility in the absence of pheromone. Pheromone was extraced from the virgin females and applied to filter paper at doses of .1, .5, and 1 female equivalent which was then introduced into containers containing 15-18 males 3 minutes prior to irradiation. Excitation and increased activity of the insects was observed when compared to the controls without the pheromone. The proportion of low percentage hatch increased with increased pheromone presence. The difference between absence and presence of pheromone was marked. It is concluded that these results are evidence of the value of this approach of preconditioning to irradiation when induction of sterility is the objective.     

Evidence for rapid speciation in African cichlid fishes

Summary Extremely rapid divergence among 7 species of African cichlid fishes is suggested by high estimates of allozymic similarity. Significant differences in gene frequencies among sympatric populations support reproductive isolation of these taxa.A portion of this study was submitted in partial fulfillment of requirments for the Ph. D from the State University of New York, Stony Brook. I thank T. D. Eccles and J. Tarbit for support and expertise, R. H. Gibbs, Jr, and V. G. Springer for review of an earlier draft, and R. K. Koehn for interest in all stages of this work. Supported in part by grants GM-25343 and GB-38662 from NIH and NSF (to RKK) and a grant-in-aid from the Society of Sigma Xi.     

The role of time series analysis in the evaluation of econometric models

This paper compares the properties of a structural model—the London Business School model of the U.K. economy—with a time series model. Information provided by this type of comparison is a useful diagnostic tool for detecting types of model misspecification. This is a more meaningful way of proceeding rather than attempting to establish the superiority of one type of model over another. In lieu of a better structural model, the effects of inappropriate dynamic specification can be reduced by combining the forecasts of both the structural and time series models. For many variables considered here these provide more accurate forecasts than each of the model types alone.     

Science and Security before the Atomic Bomb: The Loyalty Case of Harald U. Sverdrup

In the summer of 1941, Harald Sverdrup, the Norwegian-born Director of the Scripps Institution of Oceanography (SIO) in La Jolla, California, was denied security clearance to work on Navy-sponsored research in underwater acoustics applied to anti-submarine warfare. The clearance denial embarrassed the world renown oceanographer and Arctic explorer, who repeatedly offered his services to the U.S. government only to see scientists of far lesser reputation called upon to aid the war effort. The official story of Sverdrup's denial was the risk of blackmail over relatives in occupied Norway. Declassified documents tell a different story. Although Sverdrup's integrity was defended on the highest levels of U.S. science, doubt was cast upon him by members of his own institution, who accused him of being a Nazi sympathiser. Personal distrust, rooted in scientific and intellectual disagreement, spilled over into questions about Sverdrup's loyalty and judgement. These doubts were considered sufficient grounds for withholding clearance, until Roger Revelle, a former student of Sverdrup now working within the Navy, was able to obtain a limited clearance for Sverdrup to develop techniques to forecast surf conditions during amphibious assaults. After the war, this work was credited with saving many lives, but at the time it placed Sverdrup out of the mainstream of Navy-sponsored oceanographic research. In being denied access to major areas of scientific work, Sverdrup's position as a leader of American oceanography was undermined.The loyalty case of Harald Sverdrup illustrates the emergence of an institutional apparatus through which the U.S. military began to control and shape the organisation of American science in the twentieth century. Military sponsorship of scientific research, begun during the open conflicts of World War II and continuing into the simmering tensions of the Cold War, involved explicit control by the U.S. military of who had access to critical information. This in turn meant who could do science in conjunction with the military. As the U.S. Navy became the principal sponsor of oceanography in the post-war years, clearance to do military work became to a great extent clearance to do oceanography. Choices about who could be trusted were also choices about who would do science, and what kind of science they would do.     

Dynamics of estrogen binding by uterine cells in vivo

Summary The dynamics of the in vivo binding and release of tritiated estradiol in different uterine cell types are described. The very early binding of estrogens by the cytosol-nuclear and the eosinophil receptor systems is in accordance with the hypothesis that some estrogenic effects are mediated by these receptor systems.Acknowledgments. This work was supported in part by grant 2015 from the Servicio Técnico de Desarrollo Científico y Creación Artística of the University of Chile to the Laboratory of Experimental Endocrinology, Department of Experimental Morphology, University of Chile Medical School, by a Population Council Fellowship to Dr A. Tchernitchin from 1970 to 1972, by a Rockefeller Foundation grant to the Laboratories of Reproductive Biology, University of North Carolina Medical School, and by USPHS grant HD00371 to the Children's Hospital of Philadelphia. We wish to thank Drs W. E. Stumpf (Laboratories of Reproductive Biology, University of North Carolina Medical School) and A. M. Bongiovanni (Children's Hospital of Philadelphia) for the facilities available.