The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018

Global aviation operations contribute to anthropogenic climate change via a complex set of processes that lead to a net surface warming. Of importance are aviation emissions of carbon dioxide (CO₂), nitrogen oxides (NO_x), water vapor, soot and sulfate aerosols, and increased cloudiness due to contrail formation. Aviation grew strongly over the past decades (1960-2018) in terms of activity, with revenue passenger kilometers increasing from 109 to 8269 billion km yr^-1, and in terms of climate change impacts, with CO₂ emissions increasing by a factor of 6.8 to 1034 Tg CO₂ yr^-1. Over the period 2013-2018, the growth rates in both terms show a marked increase. Here, we present a new comprehensive and quantitative approach for evaluating aviation climate forcing terms. Both radiative forcing (RF) and effective radiative forcing (ERF) terms and their sums are calculated for the years 2000-2018. Contrail cirrus, consisting of linear contrails and the cirrus cloudiness arising from them, yields the largest positive net (warming) ERF term followed by CO₂ and NO_x emissions. The formation and emission of sulfate aerosol yields a negative (cooling) term. The mean contrail cirrus ERF/RF ratio of 0.42 indicates that contrail cirrus is less effective in surface warming than other terms. For 2018 the net aviation ERF is +100.9 milliwatts (mW) m^-2 (5-95% likelihood range of (55, 145)) with major contributions from contrail cirrus (57.4 mW m^-2), CO₂ (34.3 mW m^-2), and NO_x (17.5 mW m^-2). Non-CO₂ terms sum to yield a net positive (warming) ERF that accounts for more than half (66%) of the aviation net ERF in 2018. Using normalization to aviation fuel use, the contribution of global aviation in 2011 was calculated to be 3.5 (4.0, 3.4) % of the net anthropogenic ERF of 2290 (1130, 3330) mW m^-2. Uncertainty distributions (5%, 95%) show that non-CO₂ forcing terms contribute about 8 times more than CO₂ to the uncertainty in the aviation net ERF in 2018. The best estimates of the ERFs from aviation aerosol-cloud interactions for soot and sulfate remain undetermined. CO₂-warming-equivalent emissions based on global warming potentials (GWP* method) indicate that aviation emissions are currently warming the climate at approximately three times the rate of that associated with aviation CO₂ emissions alone. CO₂ and NO_x aviation emissions and cloud effects remain a continued focus of anthropogenic climate change research and policy discussions.

Distinct cellular responses induced by saporin and a transferrin-saporin conjugate in two different human glioblastoma cell lines

Glioblastoma multiforme (GBM) is the most common primary brain tumour in adults, with a median survival of ~12-18 months post-diagnosis. GBM usually recurs within 12 months post-resection, with poor prognosis. Thus, novel therapeutic strategies to target and kill GBM cells are urgently needed. The marked difference of tumour cells with respect to normal brain cells renders glioblastoma a good candidate for selective targeted therapies. Recent experimental strategies focus on over expressed cell surface receptors. Targeted toxins represent a new class of selective molecules composed by a potent protein toxin and a carrier ligand. Targeted toxins approaches against glioblastoma were under investigation in phase I and II clinical trials with several immunotoxins (IT)/ligand toxins such as IL4-Pseudomonas aeruginosa exotoxin A (IL4-PE, NBI-3001), tumour growth factor fused to PE38, a shorter PE variant, (TGF)alpha-TP-38, IL13-PE38, and a transferrin-C diphtheriae toxin mutant (Tf-CRM107). In this work, we studied the effects of the plant ribosome-inactivating saporin and of its chimera transferrin-saporin against two different GBM cell lines. The data obtained here indicate that cell proliferation is affected by the toxin treatments but that different mechanisms are used, directly linked to the presence of an active or inactive p53. A model is proposed for these alternative intracellular pathways.

Transport impacts on atmosphere and climate: Aviation

Aviation alters the composition of the atmosphere globally and can thus drive climate change and ozone depletion. The last major international assessment of these impacts was made by the Intergovernmental Panel on Climate Change (IPCC) in 1999. Here, a comprehensive updated assessment of aviation is provided. Scientific advances since the 1999 assessment have reduced key uncertainties, sharpening the quantitative evaluation, yet the basic conclusions remain the same. The climate impact of aviation is driven by long-term impacts from CO₂ emissions and shorter-term impacts from non-CO₂ emissions and effects, which include the emissions of water vapour, particles and nitrogen oxides (NO _x ). The present-day radiative forcing from aviation (2005) is estimated to be 55 mW m^-2 (excluding cirrus cloud enhancement), which represents some 3.5% (range 1.3-10%, 90% likelihood range) of current anthropogenic forcing, or 78 mW m^-2 including cirrus cloud enhancement, representing 4.9% of current forcing (range 2-14%, 90% likelihood range). According to two SRES-compatible scenarios, future forcings may increase by factors of 3-4 over 2000 levels, in 2050. The effects of aviation emissions of CO₂ on global mean surface temperature last for many hundreds of years (in common with other sources), whilst its non-CO₂ effects on temperature last for decades. Much progress has been made in the last ten years on characterizing emissions, although major uncertainties remain over the nature of particles. Emissions of NO _x result in production of ozone, a climate warming gas, and the reduction of ambient methane (a cooling effect) although the overall balance is warming, based upon current understanding. These NO _x emissions from current subsonic aviation do not appear to deplete stratospheric ozone. Despite the progress made on modelling aviation's impacts on tropospheric chemistry, there remains a significant spread in model results. The knowledge of aviation's impacts on cloudiness has also improved: a limited number of studies have demonstrated an increase in cirrus cloud attributable to aviation although the magnitude varies: however, these trend analyses may be impacted by satellite artefacts. The effect of aviation particles on clouds (with and without contrails) may give rise to either a positive forcing or a negative forcing: the modelling and the underlying processes are highly uncertain, although the overall effect of contrails and enhanced cloudiness is considered to be a positive forcing and could be substantial, compared with other effects. The debate over quantification of aviation impacts has also progressed towards studying potential mitigation and the technological and atmospheric tradeoffs. Current studies are still relatively immature and more work is required to determine optimal technological development paths, which is an aspect that atmospheric science has much to contribute. In terms of alternative fuels, liquid hydrogen represents a possibility and may reduce some of aviation's impacts on climate if the fuel is produced in a carbon-neutral way: such fuel is unlikely to be utilized until a 'hydrogen economy' develops. The introduction of biofuels as a means of reducing CO₂ impacts represents a future possibility. However, even over and above land-use concerns and greenhouse gas budget issues, aviation fuels require strict adherence to safety standards and thus require extra processing compared with biofuels destined for other sectors, where the uptake of such fuel may be more beneficial in the first instance.

Double-blind, placebo-controlled homeopathic pathogenetic trials: Symptom collection and analysis

BACKGROUND

Homeopathic pathogenetic trials (provings) are fundamental to homeopathy. Since most of the data from available provings have not been statistically evaluated, it is unclear how specific reported symptoms are and how they differ from those reported by people taking placebo.

METHOD

We combine and analyse data from two different homeopathic pathogenic trials--including 10 and 11 provers, respectively, and both including 30% placebo-to test the null hypothesis that there is no significant difference between the number of symptoms in placebo and verum groups.

RESULTS

The principal results were: Placebo reported less symptoms than verum groups. Symptom distribution according to predefined classes (common symptoms increased in intensity and/or duration-, cured, old, new and exceptional) was statistically different between placebo and verum group at a high level of significance (P<0.001). Compared to verum, placebo provers reported less new and old but more common (increased in duration or intensity) symptoms. Within repertory categories, other differences were detected. The two groups differ in terms of the duration of each symptom and kinetics of symptoms: most symptoms were more persistent in verum than in placebo groups and verum provers recorded a decreasing number of symptoms with time. Placebo provers did not show such a temporal pattern.

CONCLUSIONS

If confirmed by other studies these results would demonstrate the non-equivalence between homeopathic medicines in high dilution and placebo and contribute to the improvement of proving methodology and evaluation.

The global atmospheric environment for the next generation

Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using 26 state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, while the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models and show a reasonable agreement with surface ozone, wet deposition, and NO2 satellite observations. Large parts of the world are currently exposed to high ozone concentrations and high deposition of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 +/- 1.2 ppb (CLE) and 4.3 +/- 2.2 ppb (A2), using the ensemble mean model results and associated +/-1 sigma standard deviations. Only the progressive MFR scenario will reduce ozone, by -2.3 +/- 1.1 ppb. Climate change is expected to modify surface ozone by -0.8 +/- 0.6 ppb, with larger decreases over sea than over land. Radiative forcing by ozone increases by 63 +/- 15 and 155 +/- 37 mW m(-2) for CLE and A2, respectively, and decreases by -45 +/- 15 mW m(-2) for MFR. We compute that at present 10.1% of the global natural terrestrial ecosystems are exposed to nitrogen deposition above a critical load of 1 g N m(-2) yr(-1). These percentages increase by 2030 to 15.8% (CLE), 10.5% (MFR), and 25% (A2). This study shows the importance of enforcing current worldwide air quality legislation and the major benefits of going further. Nonattainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.

The effect of AZT and chloroquine on the activities of ricin and a saporin-transferrin chimeric toxin

This study deals with the combination of chloroquine (CQ, an anti-malaric drug) and 3'-azido-3'-deoxythymidine (AZT, anti-human immuno-deficiency virus (HIV) drug) with a chimeric toxin (TS) obtained by chemical linking of saporin (a ribosome inactivating protein from the plant Saponaria officinalis) and human transferrin, in the intoxication of the human chronic myeloid leukaemia cells (K562). Our data demonstrate that AZT, at concentrations comparable to those reached in the blood of HIV-infected patients under pharmacological treatment with this drug, can increase the toxicity of TS in cooperation with CQ inducing an increased effect on protein synthesis in K562 cells ( approximately 50% inhibition of protein synthesis for TS alone, and TS with AZT and approximately 70% with both AZT and CQ). Furthermore, pre-treatment of cells with AZT alone can induce an increase of apoptosis in K562 cells intoxicated with TS. By comparing data obtained with the model toxin ricin, we get indications that the two toxins partially differ in their intracellular routes, also suggesting that chimeric constructs containing ricin-like toxins (i.e. immunotoxins) could be coupled with the use of common and cheap drugs for the treatment of cancer in HIV-infected patients.

Vanin-1-/- mice exhibit a glutathione-mediated tissue resistance to oxidative stress

Vanin-1 is an epithelial ectoenzyme with pantetheinase activity and generating the amino-thiol cysteamine through the metabolism of pantothenic acid (vitamin B(5)). Here we show that Vanin-1(-/-) mice, which lack cysteamine in tissues, exhibit resistance to oxidative injury induced by whole-body gamma-irradiation or paraquat. This protection is correlated with reduced apoptosis and inflammation and is reversed by treating mutant animals with cystamine. The better tolerance of the Vanin-1(-/-) mice is associated with an enhanced gamma-glutamylcysteine synthetase activity in liver, probably due to the absence of cysteamine and leading to elevated stores of glutathione (GSH), the most potent cellular antioxidant. Consequently, Vanin-1(-/-) mice maintain a more reducing environment in tissue after exposure to irradiation. In normal mice, we found a stress-induced biphasic expression of Vanin-1 regulated via antioxidant response elements in its promoter region. This process should finely tune the redox environment and thus change an early inflammatory process into a late tissue repair process. We propose Vanin-1 as a key molecule to regulate the GSH-dependent response to oxidative injury in tissue at the epithelial level. Therefore, Vanin/pantetheinase inhibitors could be useful for treatment of damage due to irradiation and pro-oxidant inducers.

Biochemical and ultrastructural alterations in rat after hyperoxic treatment: effect of taurine and hypotaurine

The cell ultrastructure and some detoxifying enzyme activities were studied in skeletal muscles of young rats kept for 84 h under normobaric hyperoxia (95% O2) or normoxia as control. Rat were injected i.p.. Every 12 h either with 1 ml saline, 1 ml saline+30 mg hypotaurine or 1 ml saline+30 mg taurine. Ultrastructural observation revealed an highly protective effect on tissue damages due to hyperoxia in taurine-treated rats and, at less extent, in hypotaurine-treated ones. Enzymatic assays suggest a different mechanism of the two molecules in their protective action.

Hypotaurine protection on cell damage by singlet oxygen

Singlet oxygen (1O2), generated by irradiating methylene blue, is toxic to melanoma cell cultures. Hypotaurine is known to scavenge efficiently singlet oxygen; the addition of hypotaurine (800 microM) to the medium during irradiation of the dye produces a greater protective effect on cells than taurine added at the same concentration. The assay of some detoxifying enzymatic activities indicate a different mechanism of protection of the two molecules: taurine induces an efficient detoxifying enzymatic action with respect to the control; hypotaurine exerts its effect greatly by specifically scavenging singlet oxygen.

Vanin genes are clustered (human 6q22-24 and mouse 10A2B1) and encode isoforms of pantetheinase ectoenzymes

The mouse Vanin-1 molecule plays a role in thymic reconstitution following damage by irradiation. We recently demonstrated that it is a membrane pantetheinase (EC 3.56.1.-). This molecule is the prototypic member of a larger Vanin family encoded by at least two mouse (Vanin-1 and Vanin-3) and three human (VNN1, VNN2, VNN3) orthologous genes. We now report (1) the structural characterization of the human and mouse Vanin genes and their organization in clusters on the 6q22-24 and 10A2B1 chromosomes, respectively; (2) identification of the human VNN3 gene and the demonstration that the mouse Vanin-3 molecule is secreted by cells, and (3) that the Vanin genes encode different isoforms of the mammalian pantetheinase activity. Thus, the Vanin family represents a novel class of secreted or membrane-associated ectoenzymes. We discuss here their possible role in processes pertaining to tissue repair in the context of oxidative stress.

Pantetheinase activity of membrane-bound Vanin-1: lack of free cysteamine in tissues of Vanin-1 deficient mice

Pantetheinase (EC 3.5.1.-) is an ubiquitous enzyme which in vitro has been shown to recycle pantothenic acid (vitamin B5) and to produce cysteamine, a potent anti-oxidant. We show that the Vanin-1 gene encodes pantetheinase widely expressed in mouse tissues: (1) a pantetheinase activity is specifically expressed by Vanin-1 transfectants and is immunodepleted by specific antibodies; (2) Vanin-1 is a GPI-anchored pantetheinase, and consequently an ectoenzyme; (3) Vanin-1 null mice are deficient in membrane-bound pantetheinase activity in kidney and liver; (4) in these organs, a major metabolic consequence is the absence of detectable free cysteamine; this demonstrates that membrane-bound pantetheinase is the main source of cysteamine in tissues under physiological conditions. Since the Vanin-1 molecule was previously shown to be involved in the control of thymus reconstitution following sublethal irradiation in vivo, this raises the possibility that Vanin/pantetheinase might be involved in the regulation of some immune functions maybe in the context of the response to oxidative stress.

Is pantetheinase the actual identity of mouse and human vanin-1 proteins?

Pantetheinase is an amidohydrolase involved in the dissimilative pathway of CoA, allowing the turnover of the pantothenate moiety. We have determined the N-terminal sequence as well as the sequences of a number of tryptic and chymotryptic peptides of the protein isolated from pig kidney. These sequence stretches were used as probes to search in the SwissProt database and significant similarities were found with a GPI-anchored protein (mouse vanin-1, with a suggested role in lymphocyte migration), with two putative proteins encoded by human cDNAs (VNN1 and VNN2) and with human biotinidase. On the basis of sequence similarity, we propose that vanin-1 and VNN1 should be identified as pantetheinase.

Conformational changes at the active site of pantetheine hydrolase during denaturation by guanidine hydrochloride

Conformational changes at the active site of pantetheine hydrolase (EC3.5.1.-) during guanidine hydrochloride (GndHCl) denaturation were investigated by UV and circular dichroism spectroscopy and by electron spin resonance spectroscopy, following the spectral behaviour of the nitroxide radicals (N-(1-oxyl-2,2,5,5,-tetramethyl-3-pyrrolidinyl) iodacetamide) covalently linked to the two active site cysteine residues. At low denaturant concentrations (0.2 M) no conformational changes may be observed, whereas the catalytic activity, is strongly affected. The results indicate that the active site of pantetheine hydrolase is labile and unfolds under conditions in which no global tertiary structure modifications can be observed.

Apoptosis of Caco-2 intestinal cells invaded by Listeria monocytogenes: protective effect of lactoferrin

The apoptosis of infected hepatocytes is a critical step in nonspecific defense against Listeria monocytogenes infection. We have observed that infection by L. monocytogenes in enterocyte-like cells (Caco-2) results in apoptosis. However, a large fraction of infected intestinal epithelial cells escape from cellular condensation and fragmentation, typical of programmed cell death, and become necrotic. The balance between apoptosis and necrosis seems to be influenced by the number of internalized bacteria. The presence of 1 mg/ml of bovine lactoferrin, an iron-binding protein, added to monolayers before the bacterial infection, decreases the number of internalized bacteria and therefore the overall number of dead cells, and, more importantly, all dead cells are killed by apoptosis and not necrosis.

Effect of tunicamycin on the activity and immunoreactivity of ascorbate oxidase (Cucurbita pepo medullosa) expressed in cultured green zucchini cells

Ascorbate oxidase activity and immunoreactivity were evaluated in crude tissue extracts obtained from callus cell cultures induced by green zucchini sarcocarp and grown in the presence of tunicamycin, a powerful N-glycosylation inhibitor. Tunicamycin at 2 or 4 microg ml(-1) blocked cell growth within a couple of weeks, although a sustained cell viability was observed in the same period. A significant inhibition of total protein synthesis was observed at 10 and 15 days of culture time, with a decrease of 30% and 43% respectively when cells were grown in the presence of 2 microg ml(-1) tunicamycin, and of 48% and 57% respectively when the tunicamycin concentration was 4 microg ml(-1). After the same culture times ascorbate oxidase specific activity assayed in crude tissue extracts showed increases of about 1.9-fold and 3.5-fold (10 days) and 1.7-fold and 3.1-fold (15 days) at 2 and 4 microg ml(-1) tunicamycin, respectively. Ascorbate oxidase mRNA levels, however, did not appreciably differ between control and treated samples, measured at the same growing times. Lectin-blot, based on the use of concanavalin A, indicated a marked decrease of glycosylated proteins in tunicamycin-treated cultures. As judged by immunoblot, anti-native ascorbate oxidase antibodies scarcely recognized the enzyme expressed in tunicamycin-treated cells; on the contrary, anti-deglycosylated ascorbate oxidase antibodies were more reactive to the enzyme expressed in tunicamycin-treated cultures.

Inhibition of human placenta glutathione transferase P1-1 by the antibiotic calvatic acid and its diazocyanide analogue--evidence for multiple catalytic intermediates

The inhibition mechanism of the dimeric human placenta glutathione transferase (GST) P1-1 by calvatic acid and the reaction intermediates, i.e. the diazocyanide analogue of calvatic acid, has been investigated at pH 7.0 and 30.0 degrees C. Experiments performed at different molar ratios of inhibitor/GST P1-1 indicate that 1 mol calvatic acid inactivates 1 mol GST P1-1, containing two catalytically equivalent active sites. However, 2 mol of the diazocyanide analogue of calvatic acid inactivate 1 mol GST P1-1. Two disulfide bridges/dimer, probably between Cys47 and Cys101, have been formed during the reaction of GST P1-1 with calvatic acid and its diazocyanide analogue. The apparent second-order rate constants for GST P1-1 inactivation by calvatic acid and its diazocyanide analogue are 2.4+/-0.3 M(-1) s(-1) and (8.5+/-0.7) x 10(3) M(-1) s(-1), respectively. The reaction of calvatic acid with free L-cysteine can be described by a simple process with an apparent second-order rate constant of (5.0+/-0.4) x 10(1) M(-1) s(-1). In contrast, a transient species occurs during the reaction of the diazocyanide analogue of calvatic acid with free L-cysteine. Kinetics may be described by a second-order process [the rate constant being (8.0+/-0.5) x 10(3) M(-1) s(-1)] followed by a first-order decay [the rate constant corresponding to (1.2+/-0.1) x 10(1) s(-1)]. Calvatic acid represents an enzyme inhibitor acting much slower than its reaction intermediates (i.e. its diazocyanide analogue).

[Hemostatic status in subjects with deep venous thrombosis]

The authors report a study on the hemostatic status of a group of patients with deep venous thrombosis in order to highlight the possible pathogenetic responsibility of blood coagulative disorders in the genesis of thrombosis. The group consisted of 27 patients (14 males, 13 females, mean age 48 +/- 4 years) with deep venous thrombosis of the lower limbs (clinical symptoms were primary in 21 cases, secondary in 6 cases) diagnosed on the basis of clinical data and ultrasonographic instrumental findings. Fourteen normal subjects were also examined as a control group (12 males, 2 females, mean age 28 +/- 5 years). Venous blood was collected on fasting from patients and controls to examine the following parameters: fibrinogen (F), factor VII (F VII), antithrombin III (AT III), protein C (PC), protein S (PS) using coagulometric methods (IL), and tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI-1), fibrinopeptide A (FPA), betathromboglobulin (BTG) and dimer-D (D-D) using ELISA methods (Boehringer). Patients with deep venous thrombosis showed a significant increase in F, FVII, tPA and D-D levels compared to controls, whereas a significant reduction was observed in PAI-1. Nonsignificant variations were found for AT III, PC, PS and BTG. In the light of these results the authors affirm that: high fibrinogen and factor VII levels are highly prognostic for thrombosis in patients with deep venous thrombosis; the importance of the lack of inhibitory factors (AT III, PC, PS) is confined to individual genetically predisposed cases; there is an efficacious hyperfibrinolytic reactive response to the presence of thrombus (increase in tPA and D-D, reduction of PAI-1).

Thermal resistance of pantetheine hydrolase

Pantetheine hydrolase from pig kidney shows a very high resistance to denaturation with chemical denaturants, being unfolded at concentrations of guanidinium chloride higher than 6.5 M. On the contrary, chemical inactivation, followed by recording catalytic activity, occurs before conformational changes can be detected by fluorimetric or spectroscopic measurements. The enzyme resists temperatures as high as 80 degrees C, as monitored by second derivative spectroscopy and circular dichroism. Activity increases with temperature to an optimum of about 70 degrees C recording the initial velocity. The enzyme behaves very differently against chemical denaturants or against temperature denaturation. These results are unusual for a mesophilic protein.

Conformational changes in pantetheine hydrolase as a function of guanidinium chloride concentration

The denaturation of pantetheinase (pantetheine hydrolase, EC 3.5.1.-) was followed in guanidinium chloride using tyrosyl and tryptophanyl residues as probes in connection with change in enzymatic activity. Movements of tryptophanyl and tyrosyl residues during denaturation were studied by second-derivative and fluorescence spectroscopy and the number of these amino acids present in the protein was calculated from spectroscopic data. Pantetheinase shows a very high resistance to denaturation, being completely unfolded at guanidinium chloride concentration higher than 6.5 M. Monitoring enzymatic activity shows that inactivation of the enzyme occurred before noticeable conformational changes were detected and it is suggested that the conformation of the active site is flexible and easily perturbable compared to the protein as a whole. This inactivation is reversible, as shown by renaturation experiments. Second-derivative and fluorescence spectra showed also that tyrosyl and tryptophanyl residues are largely exposed in the native protein, confirming its hydrophobic behavior.

A kinetic study on pantetheinase inhibition by disulfides

The mammalian enzyme pantetheinase, which hydrolyzes pantetheine to pantothenic acid and cysteamine, is inhibited by many thiol reagents and activated by thiols. Two thiol groups of different reactivity and accessibility are involved in the catalytic process [Ricci, G., Nardini, M., Chiaraluce, R., Duprè, S. & Cavallini, D. (1986) Biochim. Biophys. Acta 870, 82-91]. The inhibition kinetics by some natural and synthetic disulfides [pantethine, cystamine, 5,5'-dithiobis(2-nitrobenzoic acid), 4,4'-dithiodipyridine and oxidized mercaptoethanol] has been studied by two experimental approaches, either by monitoring activity after incubation of the enzyme with the inhibitor or by determining the progress curves in the presence of substrate and inhibitor. Data reported here indicate that pantetheinase reacts irreversibly with various disulfides in a time-dependent manner with the formation of a mixed disulfide apparently preceeded by a conformational change, giving a modified E* form with new kinetic parameters. This modified form may be further competitively inhibited by disulfides interacting with the enzyme at the active site.

Exhaustive removal of N-glycans from ascorbate oxidase: effect on the enzymatic activity and immunoreactivity

Purified ascorbate oxidase from Cucurbita pepo medullosa has been subjected to enzymatic deglycosylation using peptide N-glycosidase F. Experimental conditions were chosen to obtain efficiently deglycosylated and active ascorbate oxidase: in particular, three different detergent solutions were added separately to the incubation mixtures prior to the peptide N-glycosidase F. The detergent solution made of 0.1% (w/v) sodium dodecyl sulphate + 0.5% (v/v) Nonidet P-40 proved to be the only one effective for our purpose. Our results indicate that: (i) the presence of detergents did not affect the enzymatic activity; (ii) fully deglycosylated enzyme retained its activity compared with the native form. Moreover, anti-native ascorbate oxidase antibodies scarcely recognized deglycosylated protein.

Jelly plug dissolution in Discoglossus pictus eggs (Anura) involves peroxidase-like activity and oxidative opening of disulphide bonds

In amphibian eggs the formation of a capsular chamber is one of the most striking events occurring either upon oviposition or after fertilisation. In the egg of the anuran Discoglossus pictus a capsular chamber forms following fertilisation or activation; the egg with its vitelline envelope rotates in this chamber according to gravity. Previous work showed that the chamber is the product of plug dissolution. The plug is a lens-shaped jelly coat, typical of Discoglossus, covering only part of the animal hemisphere. Its dissolution is caused by material released from the egg about 15 min after fertilisation through exocytosis of at least two types of vacuoles. Liquefaction of the plug correlates with the reduction of disulphide bonds present in the jelly matrix. In this study we investigated the nature of the substances released from the egg and some changes occurring in the plug during liquefaction. SDS-PAGE showed that the proteic profile of the plug changes dramatically after fertilisation, confirming proteic cleavage in the plug matrix during its dissolution. Through in vitro tests and electrophoretic analysis of the Ringer solution in which the egg exudate was collected, an increase in the activity of the solution was determined in the presence of hydrogen peroxide, and peroxidase activity was depicted in the egg exudate. The presence of free thiol groups and cysteic acid residues (or cysteine sulphinic acid) in the plugs of activated eggs was established, suggesting that during plug dissolution some disulphide bonds are oxidatively opened. This suggests that enzyme(s) with peroxidase activity are released following fertilisation. We surmise that such enzymes are contained in the intraovular vacuoles the exocytosis of which triggers the onset of plug liquefaction. The possible release of hydrogen peroxide from the egg is discussed.

Post-fertilization changes in Discoglossus pictus (Anura) eggs result in the formation of a capsular chamber where the egg rotates

Discoglossus pictus is one of the few anurans with an egg where a capsular chamber forms as a consequence of fertilization; the egg with its vitelline envelope rotates in this chamber according to gravity. We investigated the formation of the capsular chamber through various experimental cytochemical and ultrastructural approaches, and found that it is the product of plug liquefaction. The plug is a lens-shaped jelly coat typical of Discoglossus, and covering only part of the egg animal half. About 15 min after fertilization, granular material coming from the egg enters the plug, which gradually dissolves and, once liquefied, reorganizes itself around the entire egg, thus forming the chamber. This process goes through stages of rearrangement of the 25-A- and 250-A-thick filaments which constitute the plug matrix. The material entering the plug derives from the exocytosis of two vacuole types, with electron transparent and granular PAS-positive contents. Liquefaction of the plug correlates with the reduction of disulfide bonds present in its matrix. Furthermore, in vitro tests showed that the substances released from the egg are active in selectively dissolving only the plug, and lose activity upon boiling.

Enzymatic synthesis of S-aminoethyl-L-cysteine from pantetheine

The recently characterized compound S-aminoethylcysteine ketimine can be synthesized from purified S-aminoethylcysteine by enzymatic systems (transaminases or L-amino acid oxidase) present in mammalian tissues. S-Aminoethylcysteine, which could be considered as the natural precursor of the ketimine, is produced from L-serine and cysteamine by the action of the enzyme cystathionine-beta-synthase. We demonstrate in this paper that pantetheine, a normal cellular component, is an efficient cysteamine donor for the synthesis of S-aminoethylcysteine and of S-aminoethylcysteine ketimine in the place of free cysteamine, and we describe the enzymatic system, composed of partially purified enzymes, for the in vitro synthesis of S-aminoethylcysteine ketimine from pantetheine. This seems to indicate a new biological role for pantetheine.

Photooxidation of hypotaurine to taurine in the presence of flavins

Irradiation of organic sulfinates such as hypotaurine and cysteine sulfinic acid in the presence of catalytic amounts of flavins led to the oxidation of its sulfinic groups (-SO2H) to the corresponding sulfonates. The process of hypotaurine oxidation in the presence of riboflavin, followed by absorbance decrease at 220 nm and by ion-exchange chromatography, showed a pseudo-first-order kinetics at pH 6.0. The k value depended linearly on flavin concentrations. The reaction rate was higher at acidic pH. Although the reaction rate was not affected by the addition of superoxide dismutase or catalase, superoxide ions were supposed to be by-products of the reaction. The effectiveness of allyl alcohol as a scavenger pointed to a free-radical mechanism of the reaction. We propose a new reaction mechanism involving sulfinic radicals on this photochemical reaction.

A study on the in vitro interaction between tyrosinase and glutathione S-transferase

The actions of glutathione S-transferase and tyrosinase on the in vitro production of glutathionyl-3,4-dihydroxyphenylalanine and the dopachrome level in the presence of GSH and L-3,4-dihydroxyphenylalanine were studied. No clear evidence of complementarity between tyrosinase and glutathione S-transferase was observed; on the contrary, in the presence of glutathione S-transferase the glutathionyl-3,4-dihydroxyphenylalanine yield was lower than with tyrosinase only, as measured by HPLC. It is concluded that the spontaneous conjugation of GSH with dopaquinone should probably be high enough to scavenge the toxic quinone and to produce precursors for phaeomelanogenesis.

Circadian temporal structure evaluated by automatic monitoring

A few aspects of the circadian time structure were evaluated in a young healthy woman, with a special reference to arterial pressure and body temperature. Both parameters were estimated by the use of automatic equipments. The present study evidences the importance and the advantages of autorhythmometry (which should be applied in every instance, but can not be omitted when measuring arterial pressure) and automatic monitoring (which warrants an excellent reproducibility of measurements).