Characterization of antigen receptor response elements within the interleukin-2 enhancer.

T-cell activation and induction of interleukin-2 (IL-2) expression in human T lymphocytes require both interaction of foreign antigen with the T-cell antigen receptor and protein kinase C (PKC) stimulation. Agents such as phorbol 12-myristate 13-acetate (PMA) that stimulate PKC augment the effects of antigen but are not sufficient for IL-2 activation. By analysis of deletion mutants, we identified three DNA sequences extending from -73 to -89, -217 to -255, and -263 to -279, designated IL-2 sites A, D, and E, respectively, that are required for maximal induction of IL-2 expression. One of these regions, site E, interacted with a protein (NF-IL-2E) present only in the nuclei of cells which have been stimulated. The other two sequences interacted with a protein (NF-IL-2A) that is constitutively expressed in T cells. When multiple tandem copies of either the E site or the A site were placed upstream of the gamma-fibrinogen promoter, they activated expression via this promoter in response to signals initiated at the antigen receptor but not following PMA stimulation. For this reason, we denoted them antigen receptor response elements. The uncoupling of antigen receptor and PKC requirements in these studies indicates that these signal pathways are, at least in part, distinct and integrated at the level of the gene.     

The nucleotide sequences of barley cytoplasmic glutamate transfer RNAs and structural features essential for formation of δ-aminolevulinic acid

In chloroplasts and a number of prokaryotes, -aminolevulinic acid (ALA), the universal precursor of porphyrins, is synthesized by a multistep enzymatic pathway with glutamyl-tRNA^Glu as an intermediate. The ALA synthesizing system from barley chloroplasts is highly specific in its tRNA requirement for chloroplast tRNA^Glu; a number of other Glu-tRNAs are inactive in ALA formation although they can be glutamylated by chloroplast aminoacyl-tRNA synthetases. In order to obtain more information about the structural features defining the ability of a tRNA to be recognized by the ALA synthesizing enzymes, we purified and sequenced two cytoplasmic tRNA^Glu species from barley embryos which are inactive in ALA synthesis. By using glutamylated tRNAs as a substrate for the overall reaction, we showed that Glu-tRNA reductase is the enzyme responsible for tRNA discrimination.     

Techniques d'échanges compensés

Résumé Les échanges compensés ou counter-trade (CT) rendent possible des échanges autrement inexistants par exemple dans le cas de pays ne possédant pas l'aptitude d'organiser par leurs propres forces des actions de marketing international. Ils ont une fonction sécurisante en assurant la régulation d'échanges internationaux. Ils approfondissent une division du travail sur le plan micro-économique. Enfin ils permettent le dépassement du bilatéralisme par des techniques de troc monétisé. Les quatre plus importantes formes de CT sont: (1) le troc monétisé; (2) la compensation où un seul contrat lie le vendeur occidental à l'acheteur du Sud en même temps vendeur de biens compensés; (3) les contre-achats où deux contrats juridiquement séparés permettent l'intervention de l'assurance-crédit en faveur de l'exportateur; et enfin (4) la pré-compensation où l'achat de biens compensés précède la vente de biens d'exportation. Cette opération fait souvent appel à l'escrow-account.

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Summary Counter-trade (CT) makes trade possible where and when prevailing conditions are such that the purchase and sale of goods and/or services is not possible. It regulates the international trade. It gives certain countries the opportunity to base themselves on the experience of Western companies to open up new channels for trade. It helps the further elaboration of the international labour division in the micro-economic field. Finally it permits the overstepping of bilateralism through monetarized barter techniques. The four basic CT techiques are: (1) the monetarized barter; (2) the compensation that implies only one contract between the Western seller and the purchaser simultaneously selling compensated goods; (3) the counter-purchases that imply two juridically separated contracts so as to comply with the requirements of the insurance-credit institutions; and (4) the linked deals often using the escrow-account, where people buy first in order to sell later.

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Resumen El sistema de counter-trade permite el comercio donde y cuando las condiciones existentes son tales que la compra y venta de bienes y servicios no es posible. Este sistema regular el comercio internacional, da a ciertos países la oportunidad de basarse en la experiencia de compañias occidentales para la apertura de nuevos canales de mercado, permite una mayor división del trabajo internacional en el campo microeconómico y finalmente permite evitar el bilateralismo a través de técnicas de trueque monetarizado. Las cuatro técnicas bàsicas del sistema de counter-trade son: (1) el trueque monetarizado (2) la compensación que implica un único contrato entre el vendedor occidental y el comprador vendiendo de forma simultanea bienes compensados (3) las contra-ventas que implican dos contratos juridicamente independientes para cumplir ìsi con los requisitos de las compañías de seguros y de las entidades de crédito y (4) el uso de una cuenta especial escrow account para los contratos vinculados entre si, en la que se puede comprar primero para vender despúes.

     

The radiation response of asynchronous cells at low dose: evidence of substructure

Flow cytometry and cell sorting techniques have been used together with repeated measurement in an attempt to define better the radiation survival response of asynchronously dividing Chinese hamster V79-171 cells under aerobic and hypoxic conditions. Although the first two decades of cell inactivation have been examined, particular attention has been given to the low-dose range of a few grays, as used in individual radiation therapy treatments. A single linear-quadratic dose-response function was consistently unable to fit both the low-dose and high-dose data satisfactorily, suggesting a two-component response. Separate fitting of the low-dose and high-dose portions of the response yielded alpha and beta values which differed significantly (P = 0.001 to 0.002). The data are consistent with the hypothesis that the observed substructure simply reflects the presence of subpopulations of sensitive (G1-, G2-phase) and resistant (late S-phase) cells, which are resolved in these measurements. These results may have significance for certain situations in radiation therapy and in biophysical modeling of the radiation response.     

Male sterility and restored fertility in annual mercuries, relations with sex differentiation

The paper summarizes the researches conducted on male sterility in Mercurialis annua. Totally sterile individuals are very scarce in the dioecious species showing as the other Mercuries, unisexual flowers devoid of rudiments of the opposite sex. From one sterile male mutant, a ‘sterile series’ was conducted and genetics was studied. Sterile, semisterile, restored fertile male lines were constructed as well as female lines containing the inducer gene of male sterility, both fertility restorers and the sensitive cytoplasm. Morphology and ontogeny of these isogenic lines were presented. Male sterile anthers (empty) present a splitted tapetum and an abnormal meiotic end. Restored fertile male lines were normal. The relative abundance of auxin and cytokinins was studied. A specific cytokinin pathway measured as a background in fertile lines, the cis-oxidized pathway characterised the ‘sterile series’. Restoration of normal meiosis and tapetum appeared for the highest quantities of cis-zeatin (669 ng instead of 192 ng/100 g fresh weight in totally sterile). Auxin quantities were abundant compared with the normal males. Gene expression in the ‘sterile series’ was also compared with the fertile lines. t-RNAs specific for normal females were expressed in the male ‘sterile series’. Hybridization kinetics and in vitro translations pf poly(A)⁺RNAs demonstrate specific sequences for each line. Comparisons between identical organs (normal fertile male/restored fertile male or normal female/female of the ‘sterile series’) exhibited nearly 10% differences. The results suggest that for stamen development, a cascade of regulators probably exists: sex genes acting on the induction of stamen or pistil, then genes for sterility/restoration of fertility acting in anthers. Fertility-sterility regulators control the synthesis of a specific cytokinin pathway. The new hormonal signals are linked to several specific genes expressed in the floral morphology characterizing each line of the ‘sterile series’.     

Agonist-induced production of inositol phosphates in human airway smooth muscle cells in culture.

Smooth muscle cells (SMC) from human bronchi were isolated by elastase treatment, subcultured, and characterized by their positive reaction with a monoclonal antibody against alpha-smooth muscle actin (alpha SMA). In each cell line tested, at least 95% of the cells were positively stained. The functional properties of these cells were examined by measuring the metabolism of inositol phosphates (IPs). For that purpose, cells were incubated for 3 days before reaching confluency in the presence of myo-[3H]inositol in order to label the phosphoinositide pool, and the various [3H]IPs were separated by HPLC on a SAX column with a phosphate gradient. IP1 isomers were separated in three peaks; IP2, IP3, IP4, IP5 and IP6 (phytic acid) were each eluted as single peaks. The identity of the [3H]peaks was verified with corresponding [3H]IP standards. The accumulation of [3H]IPs was measured by incubating cells up to 30 min in the presence of 10 mM LiCl, with or without a bronchoconstrictor agent (carbachol, histamine, PGF2 alpha). Histamine, 10(-4) M, elicited a four times larger IP accumulation than carbachol, 10(-4) M, and than PGF2 alpha, 5 10(-5) M. Dose-response curves were established for histamine and carbachol in the range 10(-7)-10(-4) M. At 10(-7) M, carbachol was more effective than histamine in stimulating the IP metabolism. Atropine blocked the response to carbachol, and diphenhydramine inhibited the effect of histamine, indicating the specificity of the response to the agonists. These results indicate that cultured human bronchial SMC are a suitable preparation for studying physiological aspects of membrane transduction in the airways.     

Biphasic nature of the binding of cationic amphipaths with artificial and biological membranes

We have studied the interaction with liposomes and red cell membrane of various cationic amphipaths, chlorpromazine, methochlorpromazine, imipramine and propranolol. At low concentrations the interaction is a partition of the molecule between the lipid hydrophobic phase and the aqueous medium. The extent of the partition is dependent on the membrane composition or physical properties, on the incubation conditions (pH, ions) and on the amphipath used. After a given amount of amphipath has entered in the membrane, a new type of interaction appears which leads to an apparent saturable association. This association, which probably involves the anionic groups of the membrane components, might result from structural or/and electrical membrane perturbations induced by the presence of drug molecules between the phospholipids. Thus the interaction of a molecule of cationic amphipath with a membrane varies according to the amount of drug present.     

Effects of harmaline on ion transport and oxygen consumption by the bovine tracheal epithelium

The alkaloid harmaline is known to affect various membrane transport systems. This study examines the action of the drug on the short-circuit current (I0) and on the oxidative metabolism (Jr) in the tracheal epithelium of the cow. In this tissue I0 corresponds to the sum of two active transports: Na+ is absorbed and Cl- is secreted by a process based on the activity of the Na+ pump. A well defined relationship has been previously demonstrated between these active transports and the rate of O2 consumption (Schoenenweid et al., 1984 b). Low concentrations of harmaline (10(-6) to 5.10(-6) M) induced a small stimulation of I0. In contrast, larger concentrations (between 5.10(-5) and 10(-3) M) yielded a dose-related inhibition of I0, with an apparent concentration yielding 50% of maximal effect of 7.1.10(-4) M and maximal effect approaching 100%. The action was fully reversible after removal of the drug. The measurements of the fluxes of 22Na and 36Cl revealed that harmaline at a concentration of 8.10(-4) M, which decreased the I0 by 74 +/- 1% (n = 23), diminished both Na+ and Cl- transports, by 81 and 52%, respectively. The time course of I0 decay following the administration of harmaline was made of three components, with half-times of 0.34, 2.2 and 15.2 min. The time course was not appreciably modified when Cl- secretion was abolished with furosemide. Although harmaline, 10(-3)M, inhibited markedly I0, it did not modify Jr significantly. In contrast, when K+ in the incubation solution was omitted, both Ji and Jr were lowered.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regional Amino Acid Concentration in the Brains of Rats Exposed to High Pressures

Regional amino acid concentrations were measured in rat brain fixed by microwave irradiation at three levels of elevated atmospheric pressure corresponding to different phases of the high-pressure neurological syndrome [20 atmospheres absolute (ATA), no clinical signs; 60 ATA, tremor; 85 ATA, severe tremor and myoclonic jerks]. No changes in amino acid content occurred at 20 or 60 ATA. At 85 ATA glutamine content increased in hippocampus, striatum, cerebellum, and substantia nigra, and gamma-aminobutyric acid content increased in hippocampus. It is suggested that enhanced glutamate release in various subcortical structures contributes to the myoclonic activity observed at 85 ATA.