Aldosterone regulation of active sodium chloride transport in the lizard colon (Gallotia galloti)

Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I _sc), as well as in the mucosa-to-serosa (J _m-s ^Na ) and net sodium flux (J _net ^Na ). In AT tissues, aldosterone did not change net chloride flux (J _net ^Cl ) but did so in CT tissues. Amiloride reduced the aldosterone-increased I _sc in AT and CT tissues, inhibited J _net ^Na in AT tissues and abolished it in CT colons. J _net ^Cl was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na⁺ absorption and totally inhibited Cl^- absorption in the AT tissues, but did not change I _sc. However, in CT tissues neither Na⁺ nor Cl^- transport were affected by DIDS. A good relationship between I _sc and J _m-s ^Na was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J _net ^Na and reduced I _sc to untreated control values. Addition of serosal ouabain abolished I _sc and Na⁺ absorption in AT and CT colons, but Cl^- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT acutely treated - CT chronically treated animals - DIDS 4-4-diisothiocyanatostibene-2-2-disulfonic acid - DMSO dimethylsulphoxide - G _t tissue conductance - I _sc short circuit current - PD transepithelial potential difference - SITS 4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid - UC untreated controls Preliminary results of this paper were presented at the X ^th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990     

Identification of two distinct nuclear factors with DNA binding activity within the glucocorticoid regulatory region of the rat alpha-1-acid glycoprotein promoter

Efficient glucocorticoid induction of alpha-1-acid glycoprotein (AGP) mRNA in rat hepatoma cells HTC (JZ-1) requires the activity of one or more preexisting and labile proteins acting cooperatively with the glucocorticoid receptor. Inhibiting protein synthesis markedly diminishes the glucocorticoid induction of rat AGP mRNA without affecting the inducibility of other glucocorticoid inducible genes such as the mouse mammary tumor virus (MMTV) or tyrosine amino transferase (TAT). The sequences responsible for conferring glucocorticoid inducibility to the rat AGP gene have localized on the AGP promoter between nucleotides -121 and -42. A typical glucocorticoid regulatory element (GRE) is found between residues -121 and -105 and downstream of this are the sequences (-90 to -42) responsible for the cycloheximide inhibition of the hormonal induction (10). Using mobility shift assays we have characterized the binding of two proteins or complexes of proteins to this promoter region (-90 to -64). Our data show that the binding of these factors (called ANF-1 and ANF-2) to the DNA is highly specific, and is not directly affected by cycloheximide. Furthermore a second binding site for ANF-2 has been localized in the AGP regulatory region to a sequence that overlaps the GRE.     

Photometric or fluorometric assay of cathepsin B, L and H and papain using substrates with an aminotrifluoromethylcoumarin leaving group

N-trifluoromethylcoumarinylamide derivatives of benzyloxycarbonyl-Arg-Arg, benzyloxycarbonyl-Phe-Arg and Arg are convenient chromogenic and fluorogenic substrates of cathepsin B, L and H, respectively. Benzyloxycarbonyl-Phe-Arg-N-trifluoromethylcoumarinylamide is also a highly sensitive substrate for papain.     

Relationship between lipogenesis and glycogen synthesis in maternal and foetal tissues during late gestation in the rat. Effect of dexamethasone.

We investigated whether the polyenic and allylic phosphate systems of retinyl phosphate are essential for its mannosyl acceptor and donor activities in rat liver postnuclear membranes. Perhydromonoeneretinyl phosphate, a compound without growth-promoting activity in vitamin A-deficient animals, was prepared by catalytic hydrogenation of retinol and phosphorylation. Perhydromonoeneretinyl phosphate mannose synthesis from GDP-mannose showed continued accumulation for at least 60 min, while retinyl phosphate mannose synthesis showed a maximum at 20-30 min and then declined. Moreover, only retinyl phosphate stimulated transfer of mannose from GDP-mannose to endogenous proteins, which were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Thus, hydrogenation of side-chain double bonds in retinyl phosphate impaired only slightly its mannosyl acceptor activity, but caused loss of mannosyl donor activity.     

In Vitro Nitrogen Fixation by Two Actinomycete Strains Isolated from Casuarina Nodules

Acetylene reduction activity was demonstrated in pure cultures of two actinomycete strains isolated from nodules of Casuarina equisetifolia. This activity was comparable to that of free-living Rhizobium strains, but appeared to be less sensitive to pO₂ and more sensitive to the presence of combined nitrogen.     

Temperature dependence of the effects of some monohydric alcohols on the oxygen affinity of hemoglobin: Determination and analysis of thermodynamic parameters

We studied the effects of methanol, ethanol, iso-propanol, and n-propanol on the reaction of hemoglobin with oxygen at various temperatures. The analysis of the results in terms of the Monod-Wyman-Changeux model allowed determination of the overall contribution of the alcohols to the standard enthalpy and entropy differences between the T and R states of hemoglobin. A phenomenological approach allowed us to obtain separately the contributions related to the variations of the bulk dielectric constant of the solvent (bulk electrostatic contributions) and the contributions related to other effects (non-bulk-electrostatic contributions). The values of non-bulk-electrostatic contributions to ΔΔH and ΔΔS supported the suggestion that these contributions are mainly related to protein-solvent hydrophobic interactions.     

Optimal control of the spatial allocation of COVID-19 vaccines: Italy as a case study

While campaigns of vaccination against SARS-CoV-2 are underway across the world, communities face the challenge of a fair and effective distribution of a limited supply of doses. Current vaccine allocation strategies are based on criteria such as age or risk. In the light of strong spatial heterogeneities in disease history and transmission, we explore spatial allocation strategies as a complement to existing approaches. Given the practical constraints and complex epidemiological dynamics, designing effective vaccination strategies at a country scale is an intricate task. We propose a novel optimal control framework to derive the best possible vaccine allocation for given disease transmission projections and constraints on vaccine supply and distribution logistics. As a proof-of-concept, we couple our framework with an existing spatially explicit compartmental COVID-19 model tailored to the Italian geographic and epidemiological context. We optimize the vaccine allocation on scenarios of unfolding disease transmission across the 107 provinces of Italy, from January to April 2021. For each scenario, the optimal solution significantly outperforms alternative strategies that prioritize provinces based on incidence, population distribution, or prevalence of susceptibles. Our results suggest that the complex interplay between the mobility network and the spatial heterogeneities implies highly non-trivial prioritization strategies for effective vaccination campaigns. Our work demonstrates the potential of optimal control for complex and heterogeneous epidemiological landscapes at country, and possibly global, scales.     

The importance of being kinked: role of Pro residues in the selectivity of the helical antimicrobial peptide P5

Antimicrobial peptides (AMPs) are promising compounds for developing new antibiotic drugs against drug‐resistant bacteria. Many of them kill bacteria by perturbing their membranes but exhibit no significant toxicity towards eukaryotic cells. The identification of the features responsible for this selectivity is essential for their pharmacological development. AMPs exhibit few conserved features, but a statistical analysis of an AMP sequence database indicated that many α‐helical AMPs surprisingly have a helix‐breaking Pro residue in the middle of their sequence. To discriminate among the different possible hypotheses for the functional role of this feature, we designed an analogue of the antimicrobial peptide P5, in which the central Pro was deleted (analogue P5Del). Pro removal resulted in a dramatic increase of toxicity. This was explained by the observation that P5Del binds both charged and neutral membranes, whereas P5 has no appreciable affinity towards neutral bilayers. CD and simulative data provided a rationalization of this behavior. In solution P5, due to the presence of Pro, attains compact conformations, in which its apolar residues are partially shielded from the solvent, whereas P5Del is more helical. These structural differences reduce the hydrophobic driving force for association of P5 to neutral membranes, whereas its binding to anionic bilayers can still take place because of electrostatic attraction. After membrane binding, the Pro residue does not preclude the attainment of a membrane‐active amphiphilic helical conformation. These findings shed light on the role of Pro residues in the selectivity of AMPs and provide hints for the design of new, highly selective compounds. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Atorvastatin modifies the protein profile of circulating human monocytes after an acute coronary syndrome

Aggressive treatment with high‐dose atorvastatin reduces more effectively the incidence of cardiovascular events than moderate statin therapy. The mechanism of this benefit has not been fully elucidated. In order to know the potential effects of statin treatment on the protein expression of circulating monocytes in acute coronary syndrome (ACS) patients, a proteomic analysis of these cells was carried out by 2‐DE and MS. Twenty‐five patients with non‐ST‐elevation acute coronary syndrome (NSTEACS) were randomized, the fourth day after admission, to receive ATV 80 mg/dL (n = 14) or conventional treatment (CT) (n = 11), for two months. Blood was withdrawn at the end of the treatment, and monocytes were extracted for proteomic analysis and their protein expression patterns determined. Age, sex, total cholesterol, LDL, HDL, triglycerides, body mass index, presence of hypertension, diabetes, and smoking status were not significantly different between the two groups of patients. The expression of 20 proteins was modified by intensive ATV. Among the most relevant results stand out the normalization by intensive ATV treatment of the expression of proteins that modulate inflammation and thrombosis such as protein disulfide isomerase ER60 (PDI), Annexin I, and prohibitin, or that have other protective effects as HSP‐70. Thus, this approach shed light at the molecular level of the beneficial mechanisms of anti‐atherothrombotic drugs.