Hierarchy levels in the control of blood flow to the hind limb of the dog

In order to quantitatively assess the dynamic interactions between different levels of the O₂ transport system control hierarchy from the dynamics of the relative contribution by individual cardiovascular and respiratory variables to the response of the system to stress, flow perturbations were introduced in the hind leg of greyhounds by:1) passive motion of the biceps muscle, 2) electrical stimulation (el. stim.) of the muscle nerve, 3) el. stim. of the femoral and sciatic nerve, 4) el. stim. of the proximal end of both nerves, 5) el. stim. of the peripheral end of both nerves, 6) peripheral stimulation after autonomic blockers and 7) peripheral stimulation after Flaxedil. The following variables were continuously measured: upper and lower inflow in the biceps, inflows into the stimulated and the contralateral leg, O₂ saturation of the venous outflow from the muscle and the leg, arterial pressure, heart rate, respiratory rate and tidal volume; and their responses to perturbations were characterized by four parameters [delay time, initial slope, maximum (or minimum) and average response]. Of these, the slope was found to be the most sensitive index of stimulus specificity, while the traditionally measured steady state response, although an important consideration for performance adaptation to stress, does not permit a differentiation between the various control mechanisms which mediate the response. These results indicate that the low frequency dynamics of cardiovascular and respiratory performance contain essential information about the type of control arrangement existing at a given moment. Marked differences in both time course and magnitude of flow responses in vascular beds arranged in parallel and in series were observed with corresponding differences in the changes of the O₂ content of their respective venous outflows. From the ranking of the four parameters a numerical estimate of the overall response as well as of its peripheral and central components was obtained. Between the different experimental conditions the spectrum of the overall responses ranged from predominance of centrally mediated control mechanisms (as judged by the magnitude of the contribution by central indicators) to predominance of locally mediated control mechanism. The latter depended on the presence of increased metabolic activity. If hierarchy levels are defined functionally (rather than structurally) on the basis of the magnitude of the response of the different indicators our results show a complete reversal of the hierarchical ordering between stimulation of the proximal and peripheral end of the sciatic and femoral nerve. An appropriate choice of sufficient and adequate parameters for the characterization of integrated response pattern is a crucial prerequisite for this type of analysis.Supported by Program Project Grant HL 11747 from NHLI.     

Inter- and intramolecular transposition of Tn903.

Summary We have performed a detailed analysis of intra-and intermolecular endproducts of transposition of the compound transposon Tn903 and we show that, in our system, the transposition activity is almost entirely driven by one of the flanking insertion sequences, IS903L. The relatively inactive state of IS903R can be conferred on IS903L by changing the orientation of the internal Tn region. IS903L mediates the formation of the majority of adjacent deletions, insertion/inversions nd cointegrates, all of which are representative of replicative transposition; only a very low level of conservative transposition can be observed. Our results are discussed in relation to those showing that Tn903 uses predominantly the conservative pathway.     

Ion Channel Transport Systems from Corn Roots Reconstituted in Planar Bilayers

Ion channels from corn root microsomes were reconstituted inlipid bilayers, either black lipid membranes (BLM), or at thetip of microelectrodes, and their electrical activity characterized.Two reconstitution procedures were developped with BLM: thespontaneous detergent-mediated insertion of proteins from asuspension of ammonium sulphate precipitated proteins, a methodwhich we recently showed to work for the functional reconstitutionof the (H⁺)ATPase of plasma membrane, and the BLM formationmethod first developped by Schindler [(1980) FEBS Lett. 122:77], starting from giant proteoliposomes prepared by fusingmicrosomal vesicles with asolectin large unilamellar vesiclesvia a freeze-thaw treatment. The presence of proteins in boththe giant vesicles and the membrane forming monolayers was checked.The giant proteoliposomes were also suitable for patch-clampmeasurements via the "dip-tip" technique. We describe the voltage-dependentproperties of the channel which was routinely reconstitutedin BLM by the two methods, and we report new data concerninganother channel which was highly anion selective as evidencedby the dip-tip technique. (Received January 9, 1992; Accepted April 28, 1992)     

Marine epibiosis

Summary Polysyncraton lacazei is a colonial tunicate (family didemnidae) living in the NW-mediterranean rocky sublitoral. A thorough scanning of numerous colonies revealed that in spite of an apparently heavy local fouling pressure only one fouling species — a kamptozoan — is encountered with some regularity on Polysyncraton. We try to define the epibiotic situation of sessile marine organisms as composed of four epibiotic parameters: longevity or exposure time (A), epibiont load (E), colonizer pool (CP) and fouling-period (FP). Subsequently, these factors are combined to propose an Antifouling Potential index: AFP=(1–E/CP)×A/(FP+A). This index is intended to permit evaluating the relative antifouling defense potency to be expected in a given organism in a given epibiotic situation and to compare different cases of epibiosis and fouling.     

Modifications of microfilaments and microtubules induced by two hepatic tumor promoters,phenobarbital and biliverdin in non-transformed and transformed hepatic cell lines

Microfilaments and microtubules are components of the cytoskeleton which could be implicated in neoplastic transformation. We studied the effect of two hepatic tumor promoters, phenobarbital (PB) and biliverdin (BV), on microfilaments and microtubules of non-transformed (Cl₃) and transformed (FV) hepatic epithelial cells. Cl₃ non-transformed cells cultured in the presence of 1 × 10^–6M BV for 48 h showed a loss of F-actin, fragmentation of actin and the appearance of star-like structures in the cytoplasm, as well as loosening of the peripheral bundle of actin, and some ruffling of cell membranes. In Cl₃ cells exposed to 0.2 × 10^–3M PB a similar disappearance of F-actin staining and a very prominent ruffling of cell membrane were observed. BV and PB also produced in these cells modifications of microtubules characterized by a disappearance of centrosome staining in numerous cells, a condensed ring of tubulin around the nucleus and a depolymerized aspect of the microtubular network. All these modifications of microfilaments and microtubules closely resembled those observed in FV transformed cells in the absence of any treatment (Solvent DMSO only). We did not observe an effect of BV and PB on FV cells.The present data demonstrate that the cytoskeleton of non-transformed epithelial liver cells is sensitive to the action of liver tumor promoters suggesting that it might play a role as to yet be defined in the promotion mechanism.Abbreviations PB phenobarbital - BV biliverdin - TPA 12-0-tetradecanoyl-phorbol 13 acetate - GGT gamma-glutamyl-transpeptidase - DMSO dimethylsulfoxyde     

Preparation and anti-HIV activity of N-3 amino substituted thymidine nucleoside analogs

The N-3 amino derivatives of ddT, AZT, 3′-FddT, and D4T were prepared by electrophilic amination of the parent compounds. Although compounds , , and were essentially inactive, N-3 amino AZT (RP67042) maintained activity and displayed lower toxicity and a longer plasmatic halflife compared to AZT.     

Desipramine Elicits the Expression of Opiate Receptors and Sulfogalactosylceramide Synthesis in Rat C6 Glioma Cells

In the course of our studies on lipidoses induced by amphiphilic drugs, we have investigated the ef- of desipramine, a tricyclic antidepressant, on glial cells in culture. We noted that the addition of desipramine to the culture medium of C6 glioma cells resulted in the modification of the lipid profile of the cell membranes. Of particular interest was the presence, in the desipramine-treated cells, of an additional lipid comigrating on thin layer chromatography with sulfogalactosylceramide (S-GalCer). Addition of radiolabelled sulfuric acid in the culture medium of the desipramine-treated cells resulted in the incorporation of [35S]sulfate in the newly synthesized lipid. Furthermore, this lipid was localized selectively by indirect immunofluorescence using a specific rabbit anti-S-GalCer antibody on the cell surface of desipramine-treated, but not control, C6 cells. Desipramine also increased the activity of 3'-phosphoadenosine-5'-phosphosulfate sulfotransferase (the enzyme responsible for the synthesis of S-GalCer). Since it has been suggested that S-GalCer may be involved in opiate receptors, we looked for opiate binding sites on C6 glioma cells after exposure to desipramine. We found that dihydromorphine was able to bind to the desipramine-treated C6 cell membrane. The binding of [3H]dihydromorphine (180 fmol/mg protein) was stereospecific and had a KD of 30-60 nM. Furthermore, morphine reduced both the basal and isoproterenol-stimulated cyclic AMP levels of the desipramine-treated C6 cells. This effect was blocked by naloxone. In these respects, the opiate binding sites induced after treatment of C6 glioma cells with desipramine fulfill the requirements of a true opiate receptor.     

Most cases of medium-chain acyl-CoA dehydrogenase deficiency escape detection in France

DNA from 414 French blood donors from the Paris area was assessed for the A985G mutation responsible for most cases of autosomal recessive medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. The mutant gene frequency averaged 1/140, predicting a frequency of mutant homozygotes of 1/19 000. Discrepancy between the numbers of expected (42 per year) and recorded cases of MCAD (6 per year) suggests that most MCAD-deficient patients escape detection in France.