Steady-state kinetic studies with the polysulfonate U-9843, an HIV reverse transcriptase inhibitor

The tetramer of ethylenesulfonic acid (U-9843) is a potent inhibitor of HIV-1 RT^* and possesses excellent antiviral activity at nontoxic doses in HIV-1 infected lymphocytes grown in tissue culture. Kinetic studies of the HIV-1 RT-catalyzed RNA-directed DNA polymerase activity were carried out in order to determine if the inhibitor interacts with the template: primer or the deoxyribonucleotide triphosphate (dNTP) binding sites of the polymerase. Michaelis-Menten kinetics, which are based on the establishment of a rapid equilibrium between the enzyme and its substrates, proved inadequate for the analysis of the experimental data. The data were thus analyzed using steady-state Briggs-Haldane kinetics assuming that the template:primer binds to the enzyme first, followed by the binding of the dNTP and that the polymerase is a processive enzyme. Based on these assumptions, a velocity equation was derived which allows the calculation of all the specific forward and backward rate constants for the reactions occurring between the enzyme, its substrates and the inhibitor. The calculated rate constants are in agreement with this model and the results indicated that U-9843 acts as a noncompetitive inhibitor with respect to both the template:primer and dNTP binding sites. Hence, U-9843 exhibits the same binding affinity for the free enzyme as for the enzyme-substrate complexes and must inhibit the RT polymerase by interacting with a site distinct from the substrate binding sites. Thus, U-9843 appears to impair an event occurring after the formation of the enzyme-substrate complexes, which involves either an event leading up to the formation of the phosphoester bond, the formation of the ester bond itself or translocation of the enzyme relative to its template:primer following the formation of the ester bond.     

Thoruranium (U-236) as the extinct natural parent of thorium: The premature falsification of an essentially correct theory

To explain the origin of thorium, the Austrian geophysicist Kirsch in 1922 postulated a hypothetical isotope, thoruranium (U-236), by analogy with actinouranium. The theoretical life-time of thoruranium was predicted as being too short for it to have survived in the recent geological past. Available geological data was not inconsistent with this hypothesis, but neither did it confirm it. Within five years one new piece of geological evidence, which appeared not to conform with predictions based upon this alleged U-236, was accepted even by Kirsch as sufficient to falsify his theory. However, during the 1940s, U-236 was produced artificially, and its characteristics were found to conform with those postulated for thoruranium. Subsequent research on the origin of the universe has confirmed that indeed a natural endowment of U-236 did once exist in considerable abundance.     

Erythropoietic effects of PGE2 and 2 endoperoxide analogs

Summary The erythropoietic effects in exhypoxic polycythemic mice of two endoperoxide analogs were assessed and compared with PGE₂. The 9a, 11a epoxymethano analog (U-44069) was found to be a much more potent erythropoietic stimulus than the 11a,9a analog (U-46619) or PGE₂.This work was supported by a Senior Research Grant-in-Aid from the American Heart Association-Louisiana (DMG) and USPHS Grant No. AM 13211 (JWF).     

A new antibacterial agent (U-20,661) isolated from a streptomycete strain

Zusammenfassung Ein neues Antibiotikum, U-20661, wurde aus der Kulturflüssigkeit eines Streptomycetenstammes isoliert, welches in vitro nur gegen grampositive Bakterien wirksam ist. Die Substanz ist extrem cytotoxisch in Gewebekulturen, aber ungiftig für Mäuse.     

Sex-dependence in triglyceride metabolism in response to dietary carbohydrates.

In humans, as well as in mice, fed on high carbohydrate diets, there was a significant sex difference in the plasma tirglycerides in that males had higher levels than females. This was mainly due to the difference in their removal rate of circulating triglycerides in the animals of both sexes. In mice, males had higher levels of liver triglycerides as well as higher rate of incorporation of U- 14C-glucose into liver triglycerides when compared to females.     

Morphine tolerance in a human neuroblastoma line: Changes in choline acetylase and cholinesterase activities

Zusammenfassung Nachweis der Entstehung einer Morphin-Toleranz und-Dependenz sowie von Veränderungen (Steigerung der Cholinesterase, Verminderung der Cholin-o-Acetyltransferase) von Enzymaktivitäten nach länger dauernden Morphingaben bei Neuroblastom-Kulturen.

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Acknowledgements. This work was supported by grant No. U-2270 from the Health Research Council of the City of New York, a Lucy G. Moses Fellowship and an Irma T. Hirschl Career Scientist Award (to G.M.)     

Cholera toxin B-subunit incorporation into synaptic vesicles of the neuromuscular junction of the rat

Summary The B-subunit of cholera toxin, a nontoxic macromolecule which binds specifically to GM1 ganglioside, was conjugated to colloidal gold and injected into skeletal muscle of the rat. It was taken up rapidly in vesicles in the terminal axons at the neuromuscular junctions. Injection of albumin-colloidal gold conjugates resulted in an insignificant uptake. The results indicate that uptake of extracellular macromolecules into the terminal axon of the neuromuscular junction may be greatly enhanced by binding to gangliosides at the presynaptic membrane, and that it may occur without association with vesicular recycling related to transmitter release.The study was supported by grants from the Swedish Medical Research Council (proj. No. 07122).—Part of this study was performed at INSERM U-153, Paris, headed by Dr M. Fardeau.     

Inhibition of rat testicular monoamine oxidase activity after 250 R of whole-body X-irradiation

Résumé Chez le rat l'activité de l'oxydase testiculaire monoaminée est augmentée d'une manière significative 7 à 10 jours après une irradiation-X de 250 R du corps entier. Elle s'est abaissée au-dessous de la valeur du contrôle pendant les 153 jours qui suivirent le traitement.

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This research was sponsored by Utah State University Research Project U-300, and U.S. Atomic Energy Commission Grant No. AT(11-1)-1602.     

A polypeptide antibacterial agent isolated fromTrichoderma viride

Zusammenfassung Antibiotikum U-22324 ist ein zyklisches Peptid, das aus Kulturflüssigkeit vonTrichoderma viride isoliert wurde. Das Peptid hat die Aminosäurenzusammensetzung (GluN)₂(Glu)₁(Pro)₂(Gly)₁(Ala)₂(Dimethyl ala)₈(Val)₂(Leu)₁.     

Transport synaptosomal du Tryptophane et de la Tyrosine cérébrale. Existence de systèmes de capture d'affinité différente

Summary The existence of low and high affinity systems for tryptophan and tyrosine uptake by synaptosomes were demonstrated in vitro in the rat mesencephalon.

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Ce travail réalisé dans le laboratoire du ProfesseurM. Jouvet a bénéficié de l'aide de l'I.N.S.E.R.M. (No. U-52), de la D.R.M.E. (contrat No. 72-108) et du C.N.R.S. (Laboratoire associé No. 162).

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Nous remercions tout particulièrement MmeG. Veuillet et MmeR. Juruguen pour leur précieuse aide technique.     

Fractionation of mouse DNA by precipitation with F1 histone into fragments differing in their base composition

Summary Several fractions of mouse DNA were obtained by gradual precipitation with histone Fl. The analysis of their base composition revealed that histone interacted selectively with sequences of DNA rich in adenine plus thymine, regardless of the type of DNA molecules present in the DNA solution to be fractionated.Acknowledgments. This research was supported by the Polish Government Grant No. PRBR-1317/13.     

Geminivirus DNA replication

Geminiviruses are DNA viruses which infect plants. They have a small genome and encode only a few proteins. Therefore, their DNA replication cycle relies largely on the use of cellular DNA replication proteins. The strategy used by geminiviruses to replicate their single-stranded DNA (ssDNA) genome consists of a first stage of conversion of ssDNA into double-stranded DNA (dsDNA) intermediates and, then, the use of dsDNA as a template to amplify viral dsDNA and to produce mature ssDNA genomes by a rolling-circle replication mechanism. In addition, the accumulating evidence indicates that viral DNA replication is somehow coupled to the cell cycle regulatory network of the infected cell. For these reasons, geminiviruses are excellent model systems to understand the regulation of DNA replication and cell cycle in plant cells. Recent years have witnessed significant progress in the identification of cis-acting signals and their interaction with trans-acting factors that contribute to geminivirus origin function. These and other aspects of the geminivirus DNA replication cycle will be reviewed.     

Satellite DNA from the beetleTenebrio molitor

Summary A 142 base-pair satellite DNA from the mealworm beetle,Tenebrio molitor, has been cloned and sequenced. The satellite DNA is revealed by making a restriction digest of genomic DNA with either EcoRI or Hinfl, and constitutes approximately 49% of the genomic DNA. The presence of huge amounts of satellite DNA correlates well with the prominent blocks of heterochromatin found in tenebrionid beetles. A similar restriction digest ofXanthogaleruca luteola genomic DNA does not release a prominent satellite component.