Acute insulin infusion decreases plasma ghrelin levels in uncomplicated obesity

BACKGROUND: Plasma ghrelin levels have been shown to decrease after insulin infusion in lean subjects. Nevertheless, the mechanism of the suggested inhibitory effect of insulin on ghrelin is still unclear and no data about the effect of acute insulin infusion on plasma ghrelin concentration in obese subjects are available. OBJECTIVE: We sight to evaluate plasma ghrelin concentration during an hyperinsulinemic euglycemic clamp in uncomplicated obese subjects. METHODS: 35 uncomplicated obese subjects, body mass index (BMI) 43.3+/-10.1 kg/m(2), 33 women and 2 men, mean age 34.9+/-10, with a history of excess fat of at least 10 years underwent euglycemic hyperinsulinemic clamp. Blood samples for ghrelin were performed at baseline and steady state of euglycemic insulin clamp. RESULTS: Ghrelin concentrations decreased over time to 10.6+/-15% (range 2-39%) of baseline, from a mean of 205.53+/-93.79 pg/ml to 179.03+/-70.43 pg/ml during the clamp (95% CI, 10.69 to 36.44, P<0.01). In a univariate linear regression analysis baseline plasma ghrelin levels were inversely correlated to BMI (r=-0.564, P=0.04). A linear positive trend between whole body glucose utilization (M(FFMkg) index) and ghrelin reduction during the clamp was found (chi(2) 3.05, p=0.05). CONCLUSIONS: Our data seem to suggest that hyperinsulinemia during a euglycemic clamp is able to suppress plasma ghrelin concentrations in uncomplicated obesity. This effect appears to be positively related to insulin sensitivity.     

Toxicity of melanin-free ink of Sepia officinalis to transformed cell lines: identification of the active factor as tyrosinase

The melanin-free ink of the cephalopod Sepia officinalis is shown to contain a heat labile proteinaceous component toxic to a variety of cell lines, including PC12 cells. Gel filtration chromatography indicated that the toxic component was concentrated in those fractions eluted at a molecular weight higher than 100 kDa and exhibiting the highest tyrosinase activity. SDS-PAGE analysis of the active fractions displayed a single major band migrating at an approximate molecular weight of 100 kDa, identical with that of the single tyrosinase band in the melanin-free ink. These data unambiguously demonstrated the identity of the toxic component with tyrosinase. Treatment of purified Sepia as well as of mushroom tyrosinase with an immobilized version of proteinase K resulted in a parallel loss of tyrosinase activity and cytotoxicity. Sepia apotyrosinase was ineffective in inducing cytotoxicity in PC12 cells. Purified Sepia tyrosinase was found to induce a significant increase in caspase 3 activity in PC12 cells, leading eventually to an irreversible apoptotic process. Overall, these results disclose a hitherto unrecognized property of tyrosinase that may lead to a reappraisal of its biological significance beyond that of a mere pigment producing enzyme.     

Synthesis,characterization and X-ray structures of new antiproliferative and proapoptotic natural aldehyde thiosemicarbazones and their nickel(II) and copper(II) complexes

Synthesis and characterization of new thiosemicarbazones derived from natural aldehydes (1–9) have been investigated in order to develop a research program aimed at the development of compounds with antiviral, antibacterial, and antitumor properties. These substances contain both a chain with N and S nucleophilic centers with tuberculostatic activity, and an alkyl or terpenic moiety. In addition, a few nickel(II) and copper(II) complexes (10–18), derived also from the previously studied ligands, were synthesized and characterized by means of NMR and IR techniques. The trans-2-octenal N¹-phenylthiosemicarbazone and its nickel complex were also characterized by X-ray diffractometry. Biological studies, performed with some of these compounds, have involved both inhibition of cell proliferation and apoptosis tests in vitro on human leukemia cell line U937 to deepen our knowledge on the way these substances interfere with biological processes in leukemic cells.     

CD80+Gr-1+ myeloid cells inhibit development of antifungal Th1 immunity in mice with candidiasis

To find out whether polymorphonuclear neutrophils (PMN), abundantly recruited in disseminated Candida albicans infection, could directly affect the activation of Th cells we addressed the issues as to whether murine PMN, like their human counterparts, express costimulatory molecules and the functional consequence of this expression in terms of antifungal immune resistance. To this purpose, we assessed 1) the expression of CD80 (B7-1) and CD86 (B7-2) molecules on peripheral, splenic, and inflammatory murine Gr-1+ PMN; 2) its modulation upon interaction with C. albicans in vitro, in vivo, and in human PMN; 3) the effect of Candida exposure on the ability of murine PMN to affect CD4+ Th1 cell proliferation and cytokine production; and 4) the mechanism responsible for this effect. Murine PMN constitutively expressed CD80 molecules on both the surface and intracellularly; however, in both murine and human PMN, CD80 expression was differentially modulated upon interaction with Candida yeasts or hyphae in vitro as well as in infected mice. The expression of the CD86 molecule was neither constitutive nor inducible upon exposure to the fungus. In vitro, Gr-1+ PMN were found to inhibit the activation of IFN-gamma-producing CD4+ T cells and to induce apoptosis through a CD80/CD28-dependent mechanism. A population of CD80+Gr-1+ myeloid cells was found to be expanded in conventional as well as in bone marrow-transplanted mice with disseminated candidiasis, but its depletion increased the IFN-gamma-mediated antifungal resistance. These data indicate that alternatively activated PMN expressing CD80 may adversely affect Th1-dependent resistance in fungal infections.     

Crystal structure of yeast Cu,Zn superoxide dismutase. Crystallographic refinement at 2.5 A resolution.

The structure of Cu,Zn yeast superoxide dismutase has been determined to 2.5 A resolution. The enzyme crystallizes in the P2(1)2(1)2 space group with two dimeric enzyme molecules per asymmetric unit. The structure has been solved by molecular replacement techniques using the dimer of the bovine enzyme as the search model, and refined by molecular dynamics with crystallographic pseudo-energy terms, followed by conventional crystallographic restrained refinement. The R-factor for 32,088 unique reflections in the 10.0 to 2.5 A resolution range (98.2% of all possible reflections) is 0.158 for a model comprising two protein dimers and 516 bound solvent molecules, with a root-mean-square deviation of 0.016 A from the ideal bond lengths, and an average B-factor value of 29.9 A2. A dimeric molecule of the enzyme is composed of two identical subunits related by a non-crystallographic 2-fold axis. Each subunit (153 amino acid residues) has as its structural scaffolding a flattened antiparallel eight-stranded beta-barrel, plus three external loops. The overall three-dimensional structure is quite similar to the phylogenetically distant bovine superoxide dismutase (55% amino acid homology), the largest deviations can be observed in the regions of amino acid insertions. The major insertion site hosting residues Ser25A and Gly25B, occurs in the 2,3 beta-turn between strands 2b and 3c, resulting in the structural perturbations of the two neighbouring strands. The second insertion site, at the end of the 3c beta-strand in the wide Greek-key loop, hosts the Asn35A residue, having an evident effect on the structure of the loop and possibly on the neighbouring 5,4 beta-turn. The salt bridge Arg77-Asp99 and the disulphide bridge Cys55-Cys144 stabilize the loop regions containing the metal ligands. The stereochemistry of the two metal centres is conserved, with respect to the bovine enzyme. The Cu2+ ligands show an uneven distortion from a square plane, while Zn2+ co-ordination geometry is distorted tetrahedral. The imidazole ring of the His61 residue forms a bridge between Cu and Zn ions. A solvent peak compatible with a fifth ligand is observed 2.0 A away from the copper in the active site channel, which is filled by ordered water molecules that possibly contribute to the stability and function of the enzyme. The charged residues responsible for the electrostatic guidance of the substrate to the active site (Glu130, Glu131, Lys134 and Arg141) are fairly conserved in their positions, some of them showing different interactions in the four chains due to the intermolecular contacts between the dimers.(ABSTRACT TRUNCATED AT 400 WORDS)     

Natural variation in the appendicular skeleton of Triturus carnifex (Amphibia: Salamandridae)

Intraspecific variation in the appendicular skeleton of two geographically isolated populations of Triturus carnifex, one from northern Italy (Rosate, Milano) and one from central Italy (Bagnaia, Perugia), has been studied. A total of 1,746 forelimbs and 830 hindlimbs were examined. Forelimb skeletal variability was much greater in the Rosate than the Bagnaia population. Skeletal variants were present in 36.3% and 13.5% of the forelimbs, respectively, or in 54.7% and 22.7% of the netws (P < 0.0001). There were no predominant skeletal variants in Bagnaia, while in the Rosate population, the majority of the variants consisted of fusion of radiale and prepollicis and of phalangeal formula 1-2-3-2. Hindlimb skeletal variability was similar in the two populations and appeared to be much lower than that of the forelimb, with highly significant differences in the frequency of basipodium variants within the Rosate population and in the frequency of acropodium variants in both populations. Skeletal variants were present in about 9% of the hindlimbs, or in about 12% of the newts from either population. At present, no conclusion can be drawn about the mechanisms, genetic and/or epigenetic, underlying the skeletal variability observed in the Triturus carnifex from northern and central Italy. © 1996 Wiley-Liss, Inc.     

All-trans-retinal is a closed-state inhibitor of rod cyclic nucleotide-gated ion channels

Rod vision begins when 11-cis-retinal absorbs a photon and isomerizes to all-trans-retinal (ATR) within the photopigment, rhodopsin. Photoactivated rhodopsin triggers an enzyme cascade that lowers the concentration of cGMP, thereby closing cyclic nucleotide-gated (CNG) ion channels. After isomerization, ATR dissociates from rhodopsin, and after a bright light, this release is expected to produce a large surge of ATR near the CNG channels. Using excised patches from Xenopus oocytes, we recently showed that ATR shuts down cloned rod CNG channels, and that this inhibition occurs in the nanomolar range (aqueous concentration) at near-physiological concentrations of cGMP. Here we further characterize the ATR effect and present mechanistic information. ATR was found to decrease the apparent cGMP affinity, as well as the maximum current at saturating cGMP. When ATR was applied to outside-out patches, inhibition was much slower and less effective than when it was applied to inside-out patches, suggesting that ATR requires access to the intracellular surface of the channel or membrane. The apparent ATR affinity and maximal inhibition of heteromeric (CNGA1/CNGB1) channels was similar to that of homomeric (CNGA1) channels. Single-channel and multichannel data suggest that channel inhibition by ATR is reversible. Inhibition by ATR was not voltage dependent, and the form of its dose-response relation suggested multiple ATR molecules interacting per channel. Modeling of the data obtained with cAMP and cGMP suggests that ATR acts by interfering with the allosteric opening transition of the channel and that it prefers closed, unliganded channels. It remains to be determined whether ATR acts directly on the channel protein or instead alters channel-bilayer interactions.     

Susceptibility to Heavy Metals and Cadmium Accumulation in Aerobic and Anaerobic Thermophilic Microorganisms Isolated from Deep-Sea Hydrothermal Vents

Thirty thermophilic strains isolated from heavy metal-rich hydrothermal vent sites at Lau Basin were tested for their susceptibility to cadmium, zinc, cobalt, and nickel. The 14 aerobic spore formers belonging to the genus Bacillus, 6 anaerobic fermenters from the order Thermotogales, and 10 anaerobic sulfur reducers from the order Thermococcales could be clearly distinguished according to their metal susceptibilities. The Thermococcales were found to exhibit the highest resistance to cadmium and zinc, whereas Thermotogales were highly sensitive to these metals. In contrast, the Thermotogales displayed the highest resistance to cobalt ions. No clear distinction could be established between the metal susceptibilities of these strains and seven reference organisms used for comparative studies. Cadmium resistance, slightly inducible in some cadmium-resistant bacilli, was not plasmid mediated. The amount of cadmium immobilized by the Thermotogales was related to their level of resistance to this metal. Received: 24 February 2000 / Accepted: 28 March 2000