Management and outcomes of COVID-19 patients admitted in a newly created ICU and an expert ICU, a retrospective observational study

BACKGROUND

The COVID-19 pandemic abruptly increased the inflow of patients requiring intensive care units (ICU). French health institutions responded by a twofold capacity increase with temporary upgraded beds, supplemental beds in pre-existing ICUs, or newly created units (New-ICU). We aimed to compare outcomes according to admission in expert pre-existing ICUs or in New-ICU.

METHODS

This multicenter retrospective observational study was conducted in two 20-bed expert ICUs of a University Hospital (Expert-ICU) and in one 16-bed New-ICU in a private clinic managed respectively by 3 and 2 physicians during daytime and by one physician during the night shift. All consecutive adult patients with COVID-19-related acute hypoxemic respiratory failure admitted after centralized regional management by a dedicated crisis cell were included. The primary outcome was 180-day mortality. Propensity score matching and restricted cubic spline for predicted mortality over time were performed.

RESULTS

During the study period, 165 and 176 patients were enrolled in Expert-ICU and New-ICU respectively, 162 (98%) and 157 (89%) patients were analyzed. The unadjusted 180-day mortality was 30.8% in Expert-ICU and 28.7% in New-ICU, (log-rank test, p =  0.7). After propensity score matching, 123 pairs (76 and 78%) of patients were matched, with no significant difference in mortality (32% vs. 32%, OR 1.00 [0.89; 1.12], p = 1). Adjusted predicted mortality decreased over time (p < 0.01) in both Expert-ICU and New-ICU.

CONCLUSIONS

In COVID-19 patients with acute hypoxemic respiratory failure, hospitalization in a new ICU was not associated with mortality at day 180.

Outcomes and time trends of acute respiratory distress syndrome patients with and without liver cirrhosis: an observational cohort

BACKGROUND

In studies prior to lung-protective ventilation, liver cirrhosis in acute respiratory distress syndrome (ARDS) was associated with high mortality rates. Since patients with cirrhosis have been excluded from many trials on ARDS, their outcome when treated with lung-protective ventilation is unclear. The objectives were to assess whether cirrhosis is associated with mortality in ARDS and trends over time in mortality and severity.

METHODS

We conducted a retrospective analysis of a prospective observational cohort conducted in a 20-bed tertiary ICU from October 2003 to December 2021. All consecutive adult critically ill patients with ARDS were included. ARDS was defined by the Berlin criteria. The primary outcome was 90 day mortality, assessed with Kaplan-Meier curves and multivariate Cox analysis. Time trends were assessed on 90 day mortality, Sequential Organ-Function Assessment score (SOFA) and non-hepatic SOFA. Ventilation settings were compared between patients with and without cirrhosis.

RESULTS

Of the 7155 patients screened, 863 had a diagnosis of ARDS. Among these ARDS patients, 157(18%) had cirrhosis. The overall 90 day mortality was of 43% (378/863), 57% (90/157) in patients with cirrhosis and 41% (288/706) in patients without cirrhosis (p < 0.001). On survival curves, cirrhosis was associated with 90 day mortality (p < 0.001). Cirrhosis was independently associated with 90 day mortality in multivariate analysis (hazard ratio = 1.56, 95% confidence interval 1.20-2.02). There was no change in mortality over time in ARDS patients with and without cirrhosis. SOFA (p = 0.04) and non-hepatic SOFA (p = 0.02) increased over time in ARDS patients without cirrhosis, and remained stable in ARDS patients with cirrhosis. Tidal volume, positive end-expiratory pressure, plateau pressure and driving pressure were not different between ARDS patients with and without cirrhosis.

CONCLUSIONS

Although ARDS management improved over the last decades, the 90 day mortality remained high and stable over time for both ARDS patients with (57%) and without cirrhosis (41%). Nevertheless, the severity of patients without cirrhosis has increased over time, while the severity of patients with cirrhosis has remained stable.

Which spontaneous breathing trial to predict effort to breathe after extubation according to five critical illnesses: the cross-over GLOBAL WEAN study protocol

INTRODUCTION

Readiness to be freed from ventilatory support can be evaluated by spontaneous breathing trial (SBT) assessing the patient's ability to sustain respiratory effort after extubation. Current SBT practices are heterogenous and there are few physiological studies on the topic. The objective of this study is to assess which SBT best reproduces inspiratory effort to breathe after extubation depending on the patient's illness.

METHODS AND ANALYSIS

This will be a multicentre randomised cross-over physiological study, in a large population, in the era of modern intensive care units using last generation modern ventilators. Each included patient will perform three 15-minute SBTs in a random order: pressure support ventilation (PSV) level of 7 cmH₂O with positive end expiratory pressure (PEEP) level of 0 cmH₂O, PSV 0 cmH₂O with PEEP 0 cmH₂O and T-piece trial. A rest period of baseline state ventilation will be observed between the SBTs (10 min) and before extubation (30 min). Primary outcome will be the inspiratory muscle effort, reflected by pressure time product per minute (PTPmin). This will be calculated from oesophageal pressure measurements at baseline state, before and after each SBT and 20 min after extubation. Secondary outcomes will be PTPmin at 24 hours and 48 hours after extubation, changes in physiological variables and respiratory parameters at each step, postextubation respiratory management and the rate of successful extubation. One hundred patients with at least 24 hours of invasive mechanical ventilation will be analysed, divided into five categories of critical illness: abdominal surgery, brain injury, chest trauma, chronic obstructive pulmonary disease and miscellaneous (pneumonia, sepsis, heart disease).

ETHICS AND DISSEMINATION

The study project was approved by the appropriate ethics committee (2019-A01063-54, Comité de Protection des Personnes TOURS - Région Centre - Ouest 1, France). Informed consent is required, for all patients or surrogate in case of inability to give consent.

TRIAL REGISTRATION NUMBER

NCT04222569.

Hydroxyethyl Starch for Fluid Management in Patients Undergoing Major Abdominal Surgery: A Systematic Review With Meta-analysis and Trial Sequential Analysis

BACKGROUND

In critically ill patients, warnings about a risk of death and acute kidney injury (AKI) with hydroxyethyl starch (HES) solutions have been raised. However, HES solutions may yet have a role to play in major abdominal surgery. This meta-analysis and trial sequential analysis (TSA) aimed to investigate the effect of HES intravascular volume replacement on the risk of AKI, intraoperative blood transfusion, and postoperative intra-abdominal complications compared to crystalloid intravascular volume replacement.

METHODS

In this meta-analysis and TSA, we searched for randomized controlled trials (RCTs) comparing intraoperative HES intravascular volume replacement to crystalloid intravascular volume replacement in adult patients undergoing major abdominal surgery. Primary outcome was 30-day AKI, defined as a binary outcome according to Kidney Disease Improving Global Outcomes (KDIGO) criteria, combining stages 1, 2, and 3 into an AKI category versus no AKI category (stage 0). Secondary outcomes included rates of intraoperative blood transfusion and postoperative intra-abdominal complications. We used random effects models to calculate summary estimates. We used relative risk (RR) as summary measure for dichotomous outcomes, with corresponding 95% confidence intervals (CIs) for the primary outcome (P value <.05 was considered statistically significant) and 99% CI after Bonferroni correction for the secondary outcomes (P value <.01 was considered statistically significant).

RESULTS

Seven RCTs including 2398 patients were included. HES intravascular volume replacement was not associated with an increased risk of 30-day AKI (RR = 1.22, 95% CI, 0.94-1.59; P = .13), when compared to crystalloid intravascular volume replacement. According to TSA, this analysis was underpowered. HES intravascular volume replacement was associated with higher rates of blood transfusion (RR = 1.57 99% CI, 1.10-2.25; P = .001), and similar rates of postoperative intra-abdominal complications (RR = 0.76 99% CI, 0.57-1.02; P = .02).

CONCLUSIONS

In this meta-analysis to focus on HES intravascular volume replacement in major abdominal surgery, HES intravascular volume replacement was not associated with a higher risk of 30-day AKI when compared to crystalloid intravascular volume replacement. However, CI and TSA do not exclude harmful effects of HES intravascular volume replacement on the renal function.

Shear Wave Elastography, A New Tool for Diaphragmatic Qualitative Assessment. A Translational Study

RATIONALE

Prolonged mechanical ventilation (MV) is often associated either with a decrease (known atrophy) or an increase (supposed injury) in diaphragmatic thickness. Shear wave elastography is a non-invasive technique that measures shear modulus, a surrogate of tissue stiffness and mechanical properties.

OBJECTIVES

To describe changes in shear modulus (SM) during the ICU stay and the relationship with alterations in muscle thickness. To perform a comprehensive ultrasound-based characterization of histological and force production changes occurring in the diaphragm.

METHODS

Translational study using critically ill patients and mechanically ventilated piglets. Serial ultrasound examination of the diaphragm collecting thickness and SM was performed in both patients and piglets. Transdiaphragmatic pressure and diaphragmatic biopsies were collected in piglets.

MEASUREMENTS AND MAIN RESULTS

We enrolled 102 patients, 88 of whom were invasively mechanically ventilated. At baseline, SM was 14.3+/-4.3 kPa and diaphragm end-expiratory thickness was 2.0+/-0.5 mm. Decrease or increase by more than 10% from baseline was reported in 86% of the patients for thickness and in 92% of the patients for shear modulus. An increase in diaphragmatic thickness during the stay was associated with a decrease in SM (β=-9.34±4.41; p=0.03) after multivariable analysis. In the piglet sample, a decrease in SM over 3 days of MV was associated with loss of force production, slow and fast fiber atrophy and increased lipid droplets accumulation.

CONCLUSIONS

Increases in diaphragm thickness during critical illness is associated with decreased tissue stiffness as demonstrated by shear wave ultrasound elastography, consistent with the development of muscle injury and weakness.

Benefits of EEG-Neurofeedback on the Modulation of Impulsivity in a Sample of Cocaine and Heroin Long-Term Abstinent Inmates: A Pilot Study

The aim of this pilot study was to assess whether neurofeedback (NFB) can be useful in the treatment of impulsive behavior in long-term abstinent cocaine and heroin addicts. A single-blind sham-controlled NFB protocol was carried out to assess the effects of NFB on impulsivity in 20 (10 + 10) cocaine and heroin long-term abstinent addicts (Diagnostic and Statistical Manual of Mental Disorders [4th ed., text rev.; DSM-IV-TR]). Psychotic and neurologic diseases were excluded. Participants underwent 40 NFB sessions based on the very slow cortical potential range. Inhibitory deficits were specifically addressed through right and left prefrontal training. Clinical improvement was measured with Likert-type scales, the Hamilton Depression Rating Scale, and the State-Trait Anxiety Inventory, and impulsivity was assessed using the Barratt Impulsiveness Scale and the Continuous Performance Test. Although the results are preliminary due to the small sample size, the NFB-treated group showed a significant clinical improvement, including symptoms of anxiety and depression, with two differentiated time periods. No significant clinical improvement was found in the control group. A significant decrease in the post- versus pre-treatment measures of global impulsivity, nonplanning impulsivity, and error commission measures was found in the NFB-treated group; effect size (d_Korr) in the pre-post control design was moderate. No significant change was found in the control group. Despite the limitations of this study, the results suggest that NFB is better than placebo in improving impulsivity and clinical symptoms of anxiety and depression in long-term abstinent cocaine- and heroin-dependent individuals.

Real-time continuous monitoring of injection pressure during peripheral nerve blocks in fresh cadavers

BACKGROUND

The incidence of unintentional intraneural injection while performing peripheral nerve block has been estimated to be 15% under real-time ultrasound guidance. Injection pressure increase may detect an intraneural injection. Real-time injection pressure changes throughout an entire nerve block procedure in relationship with needle tip location have never been reported.

METHODS

A new method was developed to precisely monitor the injection pressure curve during nerve blocks, based on a miniaturised Fabbri-Perrot pressure sensor. We tested in three fresh cadavers the ability of continuous pressure monitoring to discriminate between different tissues, as the injection pressure curve ascending slope, shape and plateau pressure value depend on tissue compliance. Injections of saline were performed by an electronic syringe pump with three different constant flow rates. Pressure was measured simultaneously at the tip and in the tubing of the needle.

RESULTS

At 10 mL/min injection flow, median peak injection pressure in the intraneural group at the needle tip was 315 mmHg, while at the perineural location it was 100 mmHg (p < 0.05). Median injection pressure was 95 mmHg in the intramuscular locations group, and 819 mmHg when a muscular fascia was indented (p < 0.05). A significant difference was noted for pressure measurements between the proximal port of the needle and the tip, 625 and 417 respectively.

CONCLUSIONS

Based on significant differences in injection pressure values and curve shapes, the system was able to discriminate between four needle tip locations. This may help with needle tracking while performing a peripheral nerve block.

Aerosol sources in subway environments

Millions of people use rail subway public transport around the world, despite the relatively high particulate matter (PM) concentrations in these underground environments, requiring the identification and quantification of the aerosol source contributions to improve the air quality. An extensive aerosol monitoring campaign was carried out in eleven subway stations in the Barcelona metro system, belonging to seven subway lines. PM_2.5 samples were collected during the metro operating hours and chemically analysed to determine major and trace elements, inorganic ions, and total carbon. The chemical compositions of subway components such as brake pads, rail tracks and pantographs were also determined. The mean PM_2.5 concentrations varied widely among stations, ranging from 26 µg m^-3 to 86 µg m^-3. Subway PM_2.5 was mainly constituted by Fe₂O₃ (30-66%), followed by carbonaceous matter (18-37%) for the old stations, while for new stations equipped with Platform Screen Doors (PSD) these percentages go down to 21-44% and 15-30%, respectively. Both the absolute concentrations and the relative abundance of key species differed for each subway station, although with common patterns within a given subway line. This is a result of the different emission chemical profiles in different subway lines (using diverse types of brakes and/or pantographs). The co-emission of different sources poses a problem for their separation by receptor models. Nevertheless, receptor modelling (Positive Matrix Factorization) was applied resulting in ten sources, five of them subway-specific: RailWheel, RailWheel+Brake, Brake_A, Brake_B, Pb. The sum of their contributions accounted for 43-91% of bulk PM_2.5 for the old stations and 21-52% for the stations with PSD. The decrease of the activity during the weekends resulted in a decrease (up to 56%) in the subway-specific sources contribution to the -already lower- bulk PM_2.5 concentrations compared to weekdays. The health-related elements are mainly apportioned (> 60%) by subway sources.

Formation and alteration of airborne particles in the subway environment

Most particles in the rail subway environment are sub-micron sized ferruginous flakes and splinters generated mechanically by frictional wear of brake pads, wheels and rails. To better understand the mechanisms of formation and the alteration processes affecting inhalable particles in subways, PM samples (1-2.5 μm and 2.5-10 μm) were collected in the Barcelona Metro and then studied under a scanning electron microscope. Most particles in these samples are hematitic (up to 88%), with relatively minor amounts of mineral matter (up to 9%) and sulphates (up to 5%). Detailed microscopy (using back scattered and TEM-DRX imaging) reveals how many of the metallic particles comprise the metallic Fe nucleus surrounded by hematite (Fe₂O₃) and a coating of sulphate and chloride salts mixed with mineral matter (including Ca-carbonates, clay minerals and quartz). These observations record the emission of fine to ultrafine FePM by frictional wear at elevated temperatures that promote rapid partial (or complete) oxidation of the native metal. Water condensing on the PM surface during cooling leads to the adsorption of inorganic mineral particles that coat the iron oxide. The distinctively layered polymineralic structure that results from these processes is peculiar to particles generated in the subway environment and very different from PM typically inhaled outdoors.

The response of the different soybean metallothionein isoforms to cadmium intoxication

Cadmium is a highly toxic heavy metal for both plants and animals. The presence of Cd in agricultural soils is of major concern regarding its entry into the food chain, since Cd compounds are readily taken up by plants, and accumulated in edible parts due to their high solubility. In this study, we first demonstrate the high capacity for Cd concentration of soybean grains. Consequently, we considered the study and characterization of the molecular determinants of Cd accumulation -such as metallothioneins (MT)- to be of major practical importance. We report here the first characterization of the soybean MT system, with the identification of nine genes (one of which is a truncated pseudogene), belonging to the four plant MT types. The most highly expressed of each type was chosen for further function analysis. All of them are expressed at high levels in soybean tissues: GmMT1, GmMT2 and GmMT3 in roots, shoots and seeds, and GmMT4 only in seeds. The corresponding recombinant soybean MTs, synthesized in Escherichia coli cells cultured in metal supplemented media, exhibit greater cadmium than zinc binding capacity. These results suggest a definite role of GmMTs in Cd(II) accumulation as one of the main responses of soybean to an overload of this metal.

[The laryngeal tube]

The laryngeal tube (VBM Medizintechnic GmbH, Sulz, Germany) is a supraglottic device designed for airway management in spontaneous or positive-pressure ventilation during anesthesia or in cardiopulmonary resuscitation. Currently, the tube is available in 4 versions: the standard laryngeal tube, the disposable tube (LT-D), the dual-lumen tube (with a tube for suction) (LTS II), and the disposable LTS (LTS-D). The design of the tube has been modified several times. It is easy to insert and the airway seal is more effective than that of the laryngeal mask. The incidence of complications is similar for both devices, though use of the laryngeal tube requires more adjustments. The standard tube is somewhat less effective than the ProSeal laryngeal mask, though the new LTS II has been improved considerably. The laryngeal tube is effective as an aid to management of the difficult airway. We reviewed the literature indexed on MEDLINE through December 2006 using the search terms laryngeal tube, anesthesia, equipment, and airway.

The efficiency of potassium removal during bicarbonate hemodialysis

Patients on chronic hemodialysis often portray high serum [K+]. Although dietary excesses are evident in many cases, in others, the cause of hyperkalemia cannot be identified. In such cases, hyperkalemia could result from decreased potassium removal during dialysis. This situation could occur if alkalinization of body fluids during dialysis would drive potassium into the cell, thus decreasing the potassium gradient across the dialysis membrane. In 35 chronic hemodialysis patients, we compared two dialysis sessions performed 7 days apart. Bicarbonate or acetate as dialysate buffers were randomly assigned for the first dialysis. The buffer was switched for the second dialysis. Serum [K+], [HCO3-], and pH were measured in samples drawn before dialysis; 60, 120, 180, and 240 min into dialysis; and 60 and 90 min after dialysis. The potassium removed was measured in the dialysate. During the first 2 hr, serum [K+] decreased equally with both types of dialysates but declined more during the last 2 hr with bicarbonate dialysis. After dialysis, the serum [K+] rebounded higher with bicarbonate bringing the serum [K+] up to par with acetate. The lower serum [K+] through the second half of bicarbonate dialysis did not impair potassium removal (295.9 +/- 9.6 mmol with bicarbonate and 299.0 +/- 14.4 mmol with acetate). The measured serum K+ concentrations correlated with serum [HCO3-] and blood pH during bicarbonate dialysis but not during acetate dialysis. Alkalinization induced by bicarbonate administration may cause redistribution of K during bicarbonate dialysis but this does not impair its removal. The more marked lowering of potassium during bicarbonate dialysis occurs late in dialysis, when exchange is negligible because of a low gradient.

MTO: the second member of a Drosophila dual copper-thionein system

Drosophila MTO metal binding features were analyzed for comparison with MTN, the paralogous Drosophila metallothionein, and to classify MTO as either zinc- or copper-thionein. This was achieved by a combination of in vivo, in vitro and in silico methodologies. All the results unambiguously classified MTO as a second Drosophila copper-thionein, putting Drosophila forward as the only metazoan in which any zinc-thionein has still to be reported. Interestingly, experimental data only showed minor differences in the coordinative behavior of both MTs, but provided a characteristic spectroscopic fingerprint, revealing the possible binding of chloride anions in certain metal-MTO aggregates.

Zinc(II) is required for the in vivo and in vitro folding of mouse copper metallothionein in two domains

We postulate that zinc(II) is a keystone in the structure of physiological mouse copper metallothionein 1 (Cu-MT 1). Only when Zn(II) is coordinated does the structure of the in vivo- and in vitro-conformed Cu-MT species consist of two additive domains. Therefore, the functionally active forms of the mammalian Cu-MT may rely upon a two-domain structure. The in vitro behaviour of the whole protein is deduced from the Cu titration of the apo and Zn-containing forms and compared with that of the independent fragments using CD, UV-vis, ESI-MS and ICP-AES. We propose the formation of the following Cu, Zn-MT species during Zn/Cu replacement in Zn7-MT: (Zn4)alpha(Cu4Zn1)beta-MT, (Cu3Zn2)alpha(Cu4Zn1)beta-MT and (Cu4Zn1)alpha(Cu6)beta-MT. The cooperative formation of (Cu3Zn2)alpha(Cu4Zn1)beta-MT from (Zn4)alpha(Cu4Zn1)beta-MT indicates that the preference of Cu(I) for binding to the beta domain is only partial and not absolute, as otherwise accepted. Homometallic Cu-MT species have been obtained either from the apoform of MT or from Zn7-MT after total replacement of zinc. In these species, copper distribution cannot be inferred from the sum of the independent alpha and beta fragments. The in vivo synthesis of the entire MT in Cu-supplemented media has afforded Cu7Zn3-MT [(Cu3Zn2)alpha(Cu4Zn1)beta-MT], while that of alpha MT has rendered a mixture of Cu4Zn1-alpha MT (40%), Cu5Zn1-alpha MT (20%) and Cu7-alpha MT (40%). In the case of beta MT, a mixture of Cu6-beta MT (25%) and Cu7-beta MT (75%) was recovered [1]. These species correspond to some of those conformed in vitro and confirm that Zn(II) is essential for the in vivo folding of Cu-MT in a Cu-rich environment. A final significant issue is that common procedures used to obtain mammalian Cu6-beta MT from native sources may not be adequate.

A new insight into metallothionein (MT) classification and evolution. The in vivo and in vitro metal binding features of Homarus americanus recombinant MT

We report the synthesis and characterization of a Homarus americanus MT-cDNA (MTH) through retrotranscription of MTH-mRNA from metal-injected lobsters. Heterologous Escherichia coli expression in zinc- and copper-supplemented medium was achieved for MTH, the two domains betabetaMTH and betaalphaMTH and three site-directed mutants, betabetaC9H, betaalphaC37H, and betaalphaE31C/T34C. The in vivo conformed metal complexes and the in vitro substituted cadmium aggregates were characterized. Major stoichiometries of M(II)6-MTH for the entire MTH and M(II)3-betabetaMTH and M(II)3-betaalphaMTH for the independent domains fully validated our expression system. A low affinity binding site for a seventh Zn(II) in the in vivo synthesized MTH was located in the betaalpha domain. Additionally, minor M(II)4 species were found for each domain. Both single Cys to His mutations exhibited a similar reduction of their in vivo zinc binding ability but differed in their cadmium binding behavior when compared with the wild-type forms. Conversely, the double mutant showed an enhanced zinc and cadmium binding capacity. In vivo synthesis of MTH and of its independent domains in the presence of copper only afforded heterometallic copper-zinc species. These findings allow consideration of MTH as a zinc thionein and question the view of all crustacea MT structures as copper thioneins. Furthermore, a new approach for the evolutionary and functional classification of MT is proposed, based on the stoichiometry of metal-MT species and molecular phylogenetic analysis.

Metallothionein-III prevents glutamate and nitric oxide neurotoxicity in primary cultures of cerebellar neurons

Metallothionein (MT)-III, a member of the MT family of metal-binding proteins, is mainly expressed in the CNS and is abundant in glutamatergic neurons. Results in genetically altered mice indicate that MT-III may play neuroprotective roles in the brain, but the mechanisms through which this protein functions have not been elucidated. The aim of this work was to assess whether MT-III is able to prevent glutamate neurotoxicity and to identify the step of the neurotoxic process interfered with by MT-III. Glutamate neurotoxicity in cerebellar neurons in culture is mediated by excessive activation of glutamate receptors, increased intracellular calcium, and increased nitric oxide. It is shown that MT-III prevented glutamate- and nitric oxide-induced neurotoxicity in a dose-dependent manner, with nearly complete protection at 0.3-1 microgram/ml. MT-III did not prevent the glutamate-induced rise of intracellular calcium level but reduced significantly the nitric oxide-induced formation of cyclic GMP. Circular dichroism analysis revealed that nitric oxide triggers the release of the metals coordinated to the cysteine residues of MT-III, indicative of the S(Cys)-nitrosylation of the protein. Therefore, the present results indicate that MT-III can quench pathological levels of nitric oxide, thus preventing glutamate and nitric oxide neurotoxicity.

Drosophila MTN: a metazoan copper-thionein related to fungal forms

Two Drosophila metallothioneins (MT) have been reported: MTN, a 40 residue peptide including 10 Cys, and MTO, a 43 residue peptide including 12 Cys. However, neither functional nor evolutionary analyses for either of the Drosophila MT are available. Here, heterologous expression of Mtn in Escherichia coli is reported. The metal binding abilities of the Cu- and Zn-MTN complexes conformed in vivo, as well as the features of the Cd- and Cu-aggregates produced by metal replacement in vitro, have been determined by atomic emission spectrometry, circular dichroism and electrospray ionization mass spectrometry. Primary structure relationships with other MT have been examined. The results indicate a close resemblance of MTN to fungal copper-thioneins.

In vivo copper- and cadmium-binding ability of mammalian metallothionein beta domain

The beta domain of mouse metallothionein 1 (betaMT) was synthesized in Escherichia coli cells grown in the presence of copper or cadmium. Homogenous preparations of Cu-betaMT and Cd-betaMT were used to characterize the corresponding in vivo-conformed metal-clusters, and to compare them with the species obtained in vitro by metal replacement to a canonical Zn3-betaMT structure. The copper-containing betaMT clusters formed inside the cells were very stable. In contrast, the nascent beta peptide, although it showed cadmium binding ability, produced a highly unstable species, whose stoichiometry depended upon culture conditions. The absence of betaMT protein in E. coli protease-proficient hosts grown in cadmium-supplemented medium pointed to drastic proteolysis of a poorly folded beta peptide, somehow enhanced by the presence of cadmium. Possible functional and evolutionary implications of the bioactivity of mammalian betaMT in the presence of monovalent and divalent metal ions are discussed.

Replacement of terminal cysteine with histidine in the metallothionein alpha and beta domains maintains its binding capacity

To generate novel forms of metal-binding proteins, six mutant mouse metallothionein (MT) 1 fragments, in which a terminal cysteine residue was replaced by histidine, were expressed in Escherichia coli. The spectroscopic and analytical results showed that the alphaMT (C33H, C36H, C41H, C57H) and betaMT (C5H, C13H) mutant forms bound 4 and 3 Zn(II) atoms per molecule of protein to the nearest integer, even though in C41H and C5H, species of lower stoichiometry were also detected. In Cd(II) titrations, all the Zn(II) ions bound to the mutant proteins were displaced from the binding sites, giving rise to Cd-mutated MT forms with 4 and 3 Cd(II), respectively. However, although Cys-to-His substitutions maintained the binding capacity of the MT fragments, they caused structural changes with respect to the wild-type proteins. While C13H, C36H and C57H seem to contain Zn(II)-aggregates that are closely related to those of the wild-type proteins, only C41H and C57H gave rise to Cd(II)-aggregates similar to those of Cd4-alphaMT, where the His residue plays the role of the substituted Cys. Despite the structural implications of the Cys-to-His replacement, the dissociation constants showed no major decrease in the Cd-binding affinity in any of the mutants assayed compared with the wild-type.

A new insight into the Ag+ and Cu+ binding sites in the metallothionein beta domain

The copper(I) and silver(I) binding properties of the beta fragment of recombinant mouse metallothionein I have been studied by electronic absorption and circular dichroism spectroscopy. When possible, the stoichiometry of the species formed was confirmed by electrospray mass spectrometry. The behaviour observed differs from that reported for the native protein. Titration of either Zn3-beta MT at pH 7 or apo-beta MT at pH 3 with Cu+ leads to the formation of species having the same stoichiometry and structure: Cu6-beta MT, Cu7-beta MT and Cu10-beta MT. In the first stage of the titration of Zn3-beta MT with Cu+ at pH 7 one additional species of formula Cu4Zn1-beta MT was detected. In contrast, the titration of Zn3-beta MT at pH 7.5 and of apo-beta MT at pH 2.5 with Ag+ proceeds through different reaction pathways, affording ZnxAg3-beta MT, Ag6-beta MT and Ag9-beta MT or Ag3-beta MT, Ag6-beta MT and Ag9-beta MT, respectively. The CD envelope corresponding to species with the same stoichiometric ratio, Ag6-beta MT and Ag9-beta MT, indicates that they have a different structure at each pH value. On the basis of the differences observed, the postulated similarity between copper and silver binding to metallothionein may be questioned.

[Duodenal duplication]

Cystic duplication of the duodenum is a rare anomaly of the gastrointestinal tract. This is a report of a newborn with a cystic duplication of duodenum diagnosed prenatally. It's relevant the few clinical symptoms of a such big mass. The surgical procedure was excision of the cyst, with a good post operative curse.

Binding of excess cadmium(II) to Cd7-metallothionein from recombinant mouse Zn7-metallothionein 1. UV-VIS absorption and circular dichroism studies and theoretical location approach by surface accessibility analysis

A mouse metallotbionein (MT) 1 expression system has been constructed that renders recombinant MT as a high purity Zn-coordinated protein. Spectral changes in absorption and circular dichroism following the addition of up to 7 mol equivalents of Cd2+ to recombinant Zn7-MT showed that it behaves like the native protein. Exposure of Cd7-MT to Cd2+ resulted in further binding of these ions to the protein, although saturation was not achieved on the addition of up to 22 mol equivalents of Cd2+ to Zn7-MT. Spectral data are compatible with a model in which the first four additional Cd2+ ions are bound to Cd7-MT via sulfur atoms, and indicate that no further thiol groups are involved in the binding of the excess Cd(II) over 11. Cd2+ ions bound in excess to Cd7-MT appear to have lower binding constants as exposure of Cdn-MT (n > 7) species to Cbelex-100 retrieved Cd7-MT. Based on the X-ray data, the accessible surface areas of sulfur atoms in Cd5,Zn2-MT 2 were calculated. This led us to propose that the coordination of the first three additional Cd(II) ions to Cd7-MT proceeds by means of S-Met1-O-Met1, S-Cys7-S-Cys13 and S-Cys5-S-Cys26 pairs. Finally, comparison of the behavior of the entire MT with that of the recombinant alpha MT and beta MT subunits indicates that mutual influences may not be negligible.

Recombinant synthesis of mouse Zn3-beta and Zn4-alpha metallothionein 1 domains and characterization of their cadmium(II) binding capacity

Genetic engineering, coupled with spectroscopic analyses, has enabled the metal binding properties of the alpha and beta subunits of mouse metallothionein 1 (MT) to be characterized. A heterologous expression system in E.coli has led to high yields of their pure zinc-complexed forms. The cadmium(II) binding properties of recombinant Zn4-alpha MT and Zn3-beta MT have been studied by electronic absorption and circular dichroism. The former binds Cd(II) identically to alpha fragments obtained from mammalian organs, showing that the recombinant polypeptide behaves like the native protein. Titration of Zn3-beta MT with CdCl2 results in the formation of Cd3-beta MT. The addition of excess Cd(II) leads to Cd4-beta MT which, with the extra loading of Cd(II), unravels to give rise isodichroically to Cd9-beta MT. The effect of cadmium-displaced Zn(II) ions and excess Cd(II) above the full metal occupancy of three has been studied using Chelex-100. The Cd3-beta MT species is stable in the presence of this strong metal-chelating agent.

Structural investigation of homonuclear Pt2 and heteronuclear PdPt complexes containing a metal–metal bond bridged by hydrido and sulfido ligands

The complex [Pt2(μ-H)(μ-S)(dppe)2](PF6) undergoes a displacive order–disorder transformation at ca 230 K. The low-temperature structure is ordered with one cation–anion pair as the asymmetric unit in space group P21/n. At room temperature the b axis is halved and the space group is P2/n, imposing crystallographic twofold rotation symmetry on both ions; the anion shows major disorder and there is probably minor disorder in the cation, but its internal geometry remains essentially unchanged. The heteronuclear complex [PdPt(μ-H)(μ-S)(dppe)2](PF6) is isostructural with the Pt2 complex at room temperature. All three structures have been determined crystallographically and both complexes have been extensively characterized by NMR spectroscopy, unambiguously confirming the genuine heteronuclear nature of the mixed-metal complex and the presence of the bridging hydride ligand.