Chemical modifications of Achromobacter collagenase and their influence on the enzymic activity

A study of the influence of chemical modifications on the activity of Achromobacter iophagus collagenase (EC 3.4.24.8) has led to the following conclusions: a modification of 4 out of 80 COOH groups with carbodiimide led to 90% loss of enzymic activity. A 70% inactivation was found after modification of two tyrosines out of 30 with tetranitromethane. The modification of four to six tryptophans out of 16 with 2-hydroxy-5-nitrobenzyl bromide decreased enzyme activity to 36%. This inactivation is accelerated in the presence of collagen. An increase of reagent/enzyme molar ratio led to a modification of 16 tryptophan residues and denaturation of Acahromobacter collagenase. A modification of two arginines out of 18 with 1,2-cyclohexanedione and eight NH2 groups out of 24 with 2,3-dimethyl maleic anhydride does not change the collagenolytic activity. All NH2 groups become available for 2,3-dimethyl maleic anhydride after dissociation of the dimer. A possible analogy of hydrolytic site of collagenase with that of two other known bacterial metalloproteinases (thermolysin and Bacillus subtilis neutral proteinase (EC 3.4.24.4)) is discussed.     

Altered plasma acylcarnitine and amino acid profiles in type 2 diabetic kidney disease

Introduction

Dysregulation of acylcarnitines (AcylCNs) and amino acids metabolism have implicated in abnormality of fatty acid oxidation in type 2 diabetes (T2D). However, it is not well known whether altered plasma AcylCN, and amino acid profiles are associated with albuminuria or diabetic nephropathy (DN) in T2D.

Objective

The aim of this study was to elucidate alterations in plasma levels of AcylCNs and amino acids with respect to the T2D patients with various stages of albuminuria.

Methods

We recruited 52 healthy subjects as control, and 156 T2D patients which were divided into 52 normoalbuminuria, 52 microalbuminuria, and 52 macroalbuminuria. Plasma 37 AcylCNs and 12 amino acids were analyzed by tandem mass spectrometry.

Results

We found that T2D with normoalbuminuria and microalbuminuria had lower shot-, medium-, and long-chain AcylCNs, whereas T2D with macroalbuminuria had higher short-and medium-chain AcylCNs and lower long-chain AcylCNs than healthy subjects. Moreover, estimated glomerular filtration rate (eGFR) was a negative, independent and significant predictor of albumin to creatinine ratio (ACR) levels (β = ?0.376, P < 0.001), whereas plasma Low-density lipoprotein cholesterol (LDL-C) was significantly and positively associated with ACR levels (β = 0.169, P = 0.049). Furthermore, multivariate ordinal logistic regression analysis revealed that isobutyrylcarnitine (C4) was a positive, independent, and significant predictor of ACR levels with higher odds of having T2D patients with progression normoalbuminuria to microalbuminuria [OR = 9.93, 95 % CI (3.51–28.05), P < 0.001].

Conclusions

The findings suggest that plasma C4 may serve as a potential biomarker for the early stages of DN.

     

Molecular cytogenetics of IGH rearrangements in non-Hodgkin B-cell lymphoma

Rearrangements involving the IGH gene have been identified in about 50% of non-Hodgkin B-cell lymphomas (NHLs) and correlated to clinically relevant subgroups. However, the detection rate largely varied with the technique used. We analyzed the incidence of IGH rearrangements using several fluorescence in situ hybridization (FISH) techniques on metaphases obtained from 96 patients with nodal NHL. An IGH rearrangement was identified in 71 cases (74%). A t(14;18)(q32;q21) was found in 37 of the 42 follicular lymphomas (88.1%) studied and a t(11;14)(q13;q32) in 12 of the 14 mantle cell lymphomas (85.7%). IGH rearrangements were identified in 21 of the 40 diffuse large B-cell lymphomas (52.5%), including seven t(14;18)(q32;q21) and four t(3;14)(q27;q32). Conventional cytogenetics was uninformative in several cases. However, the complemented analysis using 24-color FISH, chromosomal whole paints, telomeric probes and locus specific identifiers enabled us to characterize complex and/or masked IGH translocations in follicular lymphomas and mantle cell lymphomas and to identify all the chromosomal partners involved in IGH rearrangements in diffuse large B-cell lymphomas. This study shows the interest of using metaphase FISH in addition to conventional cytogenetics. Following banding techniques, FISH with the IGH dual color probe can be the first approach in NHL, after which chromosome painting and 24-color FISH can be used to identify the chromosomal partners involved in IGH rearrangements. The identification of these genes is of utmost importance for a better understanding of the molecular mechanisms involved in the genesis of lymphoma.     

Identification of ypqP as a New Bacillus subtilis Biofilm Determinant That Mediates the Protection of Staphylococcus aureus against Antimicrobial Agents in Mixed-Species Communities

In most habitats, microbial life is organized in biofilms, three-dimensional edifices sustained by extracellular polymeric substances that enable bacteria to resist harsh and changing environments. Under multispecies conditions, bacteria can benefit from the polymers produced by other species (“public goods”), thus improving their survival under toxic conditions. A recent study showed that a Bacillus subtilis hospital isolate (NDmed) was able to protect Staphylococcus aureus from biocide action in multispecies biofilms. In this work, we identified ypqP, a gene whose product is required in NDmed for thick-biofilm formation on submerged surfaces and for resistance to two biocides widely used in hospitals. NDmed and S. aureus formed mixed biofilms, and both their spatial arrangement and pathogen protection were mediated by YpqP. Functional ypqP is present in other natural B. subtilis biofilm-forming isolates. However, the gene is disrupted by the SPβ prophage in the weak submerged-biofilm-forming strains NCIB3610 and 168, which are both less resistant than NDmed to the biocides tested. Furthermore, in a 168 laboratory strain cured of the SPβ prophage, the reestablishment of a functional ypqP gene led to increased thickness and resistance to biocides of the associated biofilms. We therefore propose that YpqP is a new and important determinant of B. subtilis surface biofilm architecture, protection against exposure to toxic compounds, and social behavior in bacterial communities.     

Basic studies and applications on bioremediation of DDT: A review

The persistent insecticide DDT (1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane) has been widely used for pest control in the management of mosquito-borne malaria and is still used for that purpose in some tropical countries. Considering the potential for negative effects due to DDT contamination, it is necessary to determine effective methods of remediation. Several methods have been used to degrade or transform DDT into less toxic compounds. Bacteria and white-rot fungi (WRF) have been shown to enhance the degradation process in soil using both pure and mixed cultures. Recently, a biological approach has been used as an environmentally-friendly treatment, using new biological sources to degrade DDT, e.g. brown-rot fungi (BRF), cattle manure compost (CMC) and spent mushroom waste (SMW). In this review, the abilities of BRF, CMC and SMW to degrade DDT are discussed, including the mechanisms and degradation pathways. Furthermore, application of these sources to contaminated soil is also described. The review discusses which is the best source for bioremediation of DDT.     

Context-dependent encoding of fear and extinction memories in a large-scale network model of the basal amygdala

The basal nucleus of the amygdala (BA) is involved in the formation of context-dependent conditioned fear and extinction memories. To understand the underlying neural mechanisms we developed a large-scale neuron network model of the BA, composed of excitatory and inhibitory leaky-integrate-and-fire neurons. Excitatory BA neurons received conditioned stimulus (CS)-related input from the adjacent lateral nucleus (LA) and contextual input from the hippocampus or medial prefrontal cortex (mPFC). We implemented a plasticity mechanism according to which CS and contextual synapses were potentiated if CS and contextual inputs temporally coincided on the afferents of the excitatory neurons. Our simulations revealed a differential recruitment of two distinct subpopulations of BA neurons during conditioning and extinction, mimicking the activation of experimentally observed cell populations. We propose that these two subgroups encode contextual specificity of fear and extinction memories, respectively. Mutual competition between them, mediated by feedback inhibition and driven by contextual inputs, regulates the activity in the central amygdala (CEA) thereby controlling amygdala output and fear behavior. The model makes multiple testable predictions that may advance our understanding of fear and extinction memories.     

Reinvestigation of the role of the optic vesicle in embryonic lens induction

The induction of the lens by the optic vesicle in amphibians is often cited as support for the view that a single inductive event can lead to determination in a multipotent tissue. This conclusion is based on transplantation experiments whose results indicate that many regions of embryonic ectoderm which would normally form epidermis can form a lens if brought into contact with the optic vesicle. Although additional evidence argues that during normal development other tissues, acting before the optic vesicle, also contribute to lens induction, it is still widely held, on the basis of these transplantation experiments, that the optic vesicle alone can elicit lens formation in ectoderm. While testing this conclusion by transplanting optic vesicles beneath ventral ectoderm in Xenopus laevis embryos, it became apparent that contamination of optic vesicles by presumptive lens ectoderm cells can generate lenses in these experiments, illustrating the need for adequate host and donor marking procedures. Since previous studies rarely used host and donor marking, it was not clear whether they actually demonstrated that the optic vesicle can induce lenses. Using careful host and donor marking procedures with horseradish peroxidase as a lineage tracer, we show that the optic vesicle cannot stimulate lens formation in neurula- or gastrula-stage ectoderm of Xenopus laevis. Since the general conclusion that the optic vesicle is sufficient for lens induction rests on studies in many organisms, we felt it was important to begin to test this conclusion in other amphibians as well. Similar experiments were therefore performed with Rana Palustris embryos, since it was in this organism that optic vesicle transplant studies had originally argued that this tissue alone can cause lens induction. Under conditions similar to those used in the original report, but with careful controls to assess the origin of lenses in transplants, we found that the optic vesicle alone cannot elicit lens formation. Our data lead us to propose that the optic vesicle in amphibians is not generally sufficient for lens induction. Instead, we argue that lens induction occurs by a multistep process in which an essential phase in lens determination occurs as a result of inductive interactions preceding contact of ectoderm with the optic vesicle.     

Elimination of adhering bacteria from surfaces by pulsed laser beams

As an alternative to the use of chemicals for cleaning and disinfecting surfaces of equipment in food industry, the efficacy of pulsed laser beams for removal and killing of adherent bacteria from stainless steel surfaces was assessed. Escherichia coli biofilms were produced under dynamic conditions in diluted nutritive medium incubated at 37°C for 24 h. Influence of energy density and number of shots were tested at three wavelengths (1064, 532 and 355 nm). With one 20 ns pulse, results range from 3·5 decimal reductions of the microbial load with ≤50 MW cm⁻² without visible alteration of the surface, to more than 6 decimal reductions with ≤600 MW cm⁻². The measured effect was largely attributed to removal of the micro-organisms and transfer to the surrounding air. The treatment could therefore be improved with respect to the numbers remaining associated with the surface by venting.     

Recovery processes after repeated supramaximal exercise at the altitude of 4,350m

Robach, Paul, Daniel Biou, Jean-Pierre Herry, Denis Deberne,Murielle Letournel, Jenny Vaysse, and Jean-Paul Richalet. Recoveryprocesses after repeated supramaximal exercise at the altitude of 4,350 m. J. Appl. Physiol. 82(6):1897-1904, 1997.We tested the hypothesis that prolonged exposureto high altitude would impair the restoration of muscle power duringrepeated sprints. Seven subjects performed two 20-s Wingate tests (WT1and WT2) separated by 5 min of recovery, at sea level (N) and after5-6 days at 4,350 m (H). Mean power output (MPO) andO₂ deficit were measured duringWT. O₂ uptake(O₂) and ventilation(E) were measured continuously. Blood velocity in the femoral artery (FBV) wasrecorded by Doppler ultrasound during recovery. Arterialized blood pHand concentrations of bicarbonate([HCO₃]), venousplasma lactate([La]),norepinephrine ([NE]), and epinephrine ([Epi])were measured before and after WT1 and WT2. MPO decreased between WT1and WT2 by 6.9% in N (P < 0.05) andby 10.7% in H (P < 0.01). H did not further decrease MPO. O₂ deficitdecreased between WT1 and WT2 in H only(P < 0.01). PeakO₂ after WT was reduced by30-40% in H (P < 0.01), butexcess postexercise O₂ consumptionwas not significantly lowered in H. During recovery in H compared with N, E,exercise-induced acidosis, and [NE] were higher,[Epi] tended to be higher,[La] was notaltered, and [HCO₃] andFBV were lower. The similar[La]accumulation was associated with a higher exercise-induced acidosis anda larger increase in [NE] in H. We concluded from thisstudy that prolonged exposure to high altitude did not significantly impair the restoration of muscle power during repeated sprints, despitea limitation of aerobic processes during early recovery.