Effects of butyltins and inorganic tin on chemotaxis of aquatic bacteria

Summary Tributyltin (TBT) and its degradation products dibutyltin (DBT), monobutyltin (MBT) and Sn^IV were toxic toPseudomonas fluorescens SHC-6 andSerratia sp. Gil-1 with EC₅₀ values in the range of 10^–3 to 10^–4M. These four compounds were negative chemotactic agents forP. fluorescens, and the butyltins were negatively chemotactic forSerratia sp. at concentrations over four orders of magnitude lower than the EC₅₀ values.l-Aspartate was a positive chemotactic agent for both organisms. TBT, DBT and MBT negated the effect ofl-aspartate onP. fluorescens but not onSerratia sp. Thus, TBT has the potential to affect microbial populations at concentrations much lower than those which prevent growth, and degradation of TBT does not always detoxify it. SnCl₄ was less toxic than TBT or DBT to these organisms and it was not chemotactic forSerratia sp. Gil-1. Tributylamine and tributylphosphate were less than 1/10th as toxic as TBT and they did not have a chemotactic effect on either organism at concentrations at which TBT had a significant effect. Therefore, both the Sn-and butyl-moieties contribute to the toxic and chemotactic properties of TBT.     

Oxidants act as chemorepellents in Paramecium by stimulating an electrogenic plasma membrane reductase activity

Paramecium is a valuable eukaryotic model system for studying chemosensory transduction, adaptation and cellular sensory integration. While millimolar amounts of many attractants hyperpolarize and cause faster forward swimming, oxidants are repellents that depolarize and cause backward swimming at micromolar concentrations. The non-permeant oxidants cytochrome c, nitro blue tetrazolium and ferricyanide are repellents with half maximal concentrations of 0.4 M, 2.2 M and 100 M respectively. In vivo reductase activities follow the same order of potencies. The concentration dependence of the cytochrome c reductase activity is well correlated with cytochrome c-induced depolarizations. This suggests that plasma membrane reduction of external cytochrome c is electrogenic, causing membrane depolarization and chemorepulsion. The reductase activity also appears to be voltage dependent. Depolarization by either K+, Na+, Ca+ or Mg+ correlates with inhibition of both in vivo reductase activities and cytochrome c-induced membrane potential changes. These responses were also seen in deciliated cells, showing that the body plasma membrane is sufficient for the response. Both chloroquine and diphenyleneiodonium inhibited reductase activities but only at unusually high concentrations. This activity showed no pH dependence in the physiological range. We propose that a plasma membrane bound NADPH-dependent reductase controls oxidant-induced depolarizations and consequent chemorepulsion.Abbreviations bmv Body plasma membrane vesicles - BPS Bathophenanthroline disulfonate - cAMP Cyclic adenosine monophosphate - cmv Ciliary membrane vesicles - cyt c Cytochrome c - DPI Diphenyleneiodonium - EC ₅₀ Concentration for 50% effectiveness - FeCN Ferricyanide [Fe(CN)₆–3] - FeEDTA Ethylenediaminetetracetic acid (ferric-sodium salt) - GTP Guanosine 5-triphosphate - KCN Potassium cyanide - mM Millimolar - MOPS 3-(N-morpholino) propanesulfonic acid - mV Millivolts - NADH Nicotinamide adenine dinucleotide (reduced form) - NADPH Nicotinamide adenine dinucleotide phosphate (reduced form) - NBT Nitro blue tetrazolium - nm Nanometer - pCMB p-Chloromercuribenzoate - PMA Phorbol 12-myristate 13-acetate - s.d. Standard deviation - SOD Superoxide dismutase - Tris Tris(hydroxymethyl)aminomethane - M Micromolar     

The effects of interleukin-1 therapy on peripheral blood granulocyte function in humans

During a phase I trial of interleukin-1 (IL-1) in patients with ovarian carcinomas, the effects of this treatment on blood granulocyte respiratory burst and locomotive responses were examined. Differences in baseline granulocyte function in patients as well as dose-related effects of IL-1 treatment were observed. Patients enrolled early in the trial (low-dose patients) had significantly lower locomotive responses before treatment than their paired controls; these low responses normalized after 5 days of continuous-infusion IL-1 treatment. Patients enrolled later (high-dose patients) had normal locomotive responses before treatment and IL-1 treatment was associated with suppression of responses to selected stimuli at the end of treatment. Pretreatment respiratory burst responses in both low-and high-dose patient groups were essentially normal, but the rates of granulocyte H₂O₂ production following phorbol myristate acetate stimulation became significantly less than control values at the end of treatment. In vitro exposure of either patient or control cells to 150 U/ml IL-1 did not alter their locomotive or respiratory burst responses, suggesting the observed in vivo effects were not mediated directly by IL-1. Treatment with IL-1 is associated with changes in ex vivo granulocyte function that are related to the IL-1 dose. Treatment with low doses of IL-1 may provide a means of normalizing abnormal polymorphonuclear leukocyte function in some patients with ovarian malignancies.     

凤眼莲根分泌物氨基酸组分对根际肠杆菌属F2细菌的趋化作用

凤眼莲(Eichhornia crassipes)的根分泌物中含有Met等多种氨基酸,其中Met、GABA、Gly、Ala、Asp、Ser、Val和Leu(10^-7～10^-2mol·L^-1)均对凤眼莲的根际肠杆菌属F₂(Enterobacter sp.F₂)细菌有强烈的正趋化作用;Glu、Thr和His(10^-7～10^-3mol·L^-1)也对该菌有一定的正趋化作用;而Lys、Cys、Arg、Tyr、Pro、Asn、Gln、Ile、Phe和Typ则对该菌表现出一定的负趋化作用.对细菌的正趋化作用存在一个趋化物的最适浓度范围.具有正趋化作用的氨基酸在凤眼莲根际的浓度都较高,而具有负趋化作用的浓度则较低,这正是凤眼莲与该根际细菌结合为根际微生态系统的原因之一.     

Trichinella spiralis: Generation in the presence of rat serum of factors chemotactic for rat cells

Chemotaxis of rat peritoneal cells, of which the eosinophil was the predominant migratory cell type, toward incubates of Trichinella spiralis was studied using a modified Boyden chamber. Excysted muscle larvae, preadults, and adults were incubated in a buffered medium for 20 hr at 37 C. Worms were incubated alone or with serum or spleen cells, or both, from immune and nonimmune rats. Incubates of worm stages alone possessed no chemotactic activity as compared with incubation medium as a negative control and zymosan-activated serum as a positive control. Both normal and immune sera tested alone stimulated cell migration to the same degree. Incubates of spleen cells from either normal or immunized hosts did not show chemotactic activity. Chemotaxis caused by normal and immune sera were not altered by incubation with homologous spleen cells. Addition of larva, preadults, and adult worms to sera, however, enhanced chemotactic activity over sera alone. Chemotaxis caused by larvae plus immune sera was significantly greater than that stimulated by larvae plus normal sera. This difference decreased when preadults were substituted for larvae and was not observed when adult worms were used. Reversal of the chemical gradients showed that active cell migration caused by various incubates was due to Chemotaxis.     

Proton-motive force and the motile behavior of Bacillus subtilis

Changes in the proton-motive force cause a transient change in the motile behavior of Bacillus subtilis cells. Both an increase and a decrease in the proton-motive force cause transient tumbling. Simultaneous decrease of proton-motive force and increase of attractant concentration lessens the response toward the attractant. A simultaneous increase of proton-motive force and increase of attractant concentration prolonges the response toward attractant. A hypothesis explaining the various effects is given.Abbreviations KT medium potassium taxis medium - NaT medium sodium taxis medium - HT medium acidic taxis medium - OHT medium alkaline taxis medium - DNP 2,4-dinitrophenol     

Chemotaxis with directional sensing during Dictyostelium aggregation

We show that the chemotactic movements of colonies of the starving amoeba Dictyostelium discoideum are driven by a force that depends on both the direction of propagation (directional sensing) of reaction-diffusion chemotactic waves and on the gradient of the concentration of the chemoattractant, solving the chemotactic wave paradox. It is shown that the directional sensing of amoebae is due to the sensitivity of the cells to the time variation of the concentration of the chemoattractant combined with its spatial gradient. It is also shown that chemotaxis exclusively driven by local concentration gradient leads to unstable local motion, preventing cells from aggregation. These findings show that the formation of mounds, which initiate multicellularity in Dictyostelium discoideum, is caused by the sensitivity of the amoebae due to three factors, namely, to the direction of propagation of the chemoattractant, to its spatial gradient, and to the emergence of cAMP “emitting centres”, responsible for the local accumulation of the amoebae.     

Self-electroporation as a Model for Fusion Pore Formation

Abstract

The creation of a small opening called the fusion pore is a necessary prerequisite for neurotransmitter release from synaptic vesicles. It is known that high intensity electric fields can create pores in vesicles by a process called electroporation. Due to the presence of charged phosphatidylserine (PS) molecules on the inner leaflet of the cell membrane, an electric field that is strong enough to cause electroporation of a synaptic vesicle might be present. It was shown by K. Rosenheck [K. Rosenheck. Biophys J 75, 1237–1243 (1998)] that in a planar geometry, fields sufficient to cause electroporation can occur at intermembrane separations of less than ～3 nm. It is frequently found, however, that the cell membrane is not planar but caves inward at the locations where a vesicle is close to it. Indentation of the cell membrane in the fusion region was modelled as a hemisphere and a theoretical study of the electric field in the vicinity of the cell membrane taking into account the screening effect of dissolved ions in the cytoplasm was performed. It was discovered that fields crossing the electroporation threshold occurred at a distance of 2 nm or less, supporting the claim that electroporation could be a possible mechanism for fusion pore formation.     

Neutralizing Nanobodies Targeting Diverse Chemokines Effectively Inhibit Chemokine Function

Chemokine receptors and their ligands play a prominent role in immune regulation but many have also been implicated in inflammatory diseases such as multiple sclerosis, rheumatoid arthritis, allograft rejection after transplantation, and also in cancer metastasis. Most approaches to therapeutically target the chemokine system involve targeting of chemokine receptors with low molecular weight antagonists. Here we describe the selection and characterization of an unprecedented large and diverse panel of neutralizing Nanobodies (single domain camelid antibodies fragment) directed against several chemokines. We show that the Nanobodies directed against CCL2 (MCP-1), CCL5 (RANTES), CXCL11 (I-TAC), and CXCL12 (SDF-1α) bind the chemokines with high affinity (at nanomolar concentration), thereby blocking receptor binding, inhibiting chemokine-induced receptor activation as well as chemotaxis. Together, we show that neutralizing Nanobodies can be selected efficiently for effective and specific therapeutic treatment against a wide range of immune and inflammatory diseases.