Identification by monoclonal antibodies of a new epitope in the glycoprotein complex of Sindbis virus

Monoclonal antibodies against a deletion mutant of Sindbis virus were produced and characterized in order to determine the fine mapping and functional activities of single viral epitopes. All monoclonal antibodies so far tested showed a certain degree of reciprocal competition and were directed against an antigenic determinant which was present only on the undissociated complex of the E1 and E2 glycoproteins. A biological assay measuring viral haemagglutination showed no decrease in the titre of viral samples preincubated with monoclonal antibodies. Conversely, a reduction in viral infectivity was demonstrated, particularly with two of these antibodies. The results suggest that the antibodies which we characterized seem to recognize a new epitope which is represented on both glycoproteins on the surface of this mutant of Sindbis virus.

Surface Modification of Polyimide Thin Films for Peripheral Invasive Neural Interfaces

Despite recognized as one key component for establishing a functional electrical connection with nerves, neural invasive peripheral interfaces are still not optimal for long-term applications in humans. An improvement in the field of biocompatible and non-toxic materials is necessary to overcome the issues of interface/tissue mismatch and physiological reactions. The present work aimed to study, implement and characterize a novel approach to modify the surface of neural mi-crolectrodes basedon polyimide thin films. The purpose was to improve biocompatibility and to promote neuronal migration, growth and differentiation by increasing the surface roughness and endowing the surface with structure-reactivity for thiol-containing amino acids or peptides. L-Cysteine-Rhodamine B, used as a model biomolecule, was successfully grafted on samples surface via the introduction of cross-linkable vinyl groups on polyimide foils. Preliminary in vitro biological analysis allowed to evaluate the tendency of PC12 cells to adhere and to proliferate.

Ultrastructural and biochemical evidence that the L929 cell retrovirus lacks the env gene translation product

LCV, a murine retrovirus released by L929 mouse cell fibroblasts, is non-infectious when inoculated into SC-1, mink, D-17 or Vero cells. Ultrastructural examination by thin sectioning, freeze-etching or negative staining revealed the absence, on the viral envelope, of the radially disposed spikes. Polyacrylamide gel electrophoresis of radiolabelled viral components showed the absence of the glycosylated protein gp70 as well as of the p15E cleavage product of the polyprotein precursor gPr90env. The premature loss of the gp70 molecule from LCV to the culture medium was ruled out since no peak of D-[14C]glucosamine-labelled glycoprotein was detected by affinity chromatography or immunoprecipitation of concentrated medium. The ultrastructural and biochemical results all supported the hypothesis that the absence of infectivity was due to the lack of gp70 glycoprotein in the envelope of LCV. A possible block at a translational or post-translational level was also investigated by immunofluorescence studies with antisera directed against ecotropic or xenotropic gp70; Moloney murine leukaemia virus-infected or NZB cells were used as positive controls for eco- or xenotropic viruses respectively. The absence of fluorescent stain in L929 cells further supported these results and suggested that LCV and the L929 parental cell line lack the uncleaved precursor and the final product of the env gene translation process.

Global-mean temperature change from shipping toward 2050: improved representation of the indirect aerosol effect in simple climate models

We utilize a range of emission scenarios for shipping to determine the induced global-mean radiative forcing and temperature change. Ship emission scenarios consistent with the new regulations on nitrogen oxides (NO(x)) and sulfur dioxide (SO(2)) from the International Maritime Organization and two of the Representative Concentration Pathways are used as input to a simple climate model (SCM). Based on a complex aerosol-climate model we develop and test new parametrizations of the indirect aerosol effect (IAE) in the SCM that account for nonlinearities in radiative forcing of ship-induced IAE. We find that shipping causes a net global cooling impact throughout the period 1900-2050 across all parametrizations and scenarios. However, calculated total net global-mean temperature change in 2050 ranges from -0.03[-0.07,-0.002]°C to -0.3[-0.6,-0.2]°C in the A1B scenario. This wide range across parametrizations emphasizes the importance of properly representing the IAE in SCMs and to reflect the uncertainties from complex global models. Furthermore, our calculations show that the future ship-induced temperature response is likely a continued cooling if SO(2) and NO(x) emissions continue to increase due to a strong increase in activity, despite current emission regulations. However, such cooling does not negate the need for continued efforts to reduce CO(2) emissions, since residual warming from CO(2) is long-lived.

Properties and Processing of Aviation Exhaust Aerosol at Cruise Altitude Observed from the IAGOS-CARIBIC Flying Laboratory

The characteristics of aviation-induced aerosol, its processing, and effects on cirrus clouds and climate are still associated with large uncertainties. Properties of aviation-induced aerosol, however, are crucially needed for the assessment of aviation's climate impacts today and in the future. We identified more than 1100 aircraft plume encounters during passenger aircraft flights of the IAGOS-CARIBIC Flying Laboratory from July 2018 to March 2020. The aerosol properties inside aircraft plumes were similar, independent of the altitude (i.e., upper troposphere, tropopause region, and lowermost stratosphere). The exhaust aerosol was found to be mostly externally mixed compared to the internally mixed background aerosol, even at a plume age of 1 to 3 h. No enhancement of accumulation mode particles (diameter >250 nm) could be detected inside the aircraft plumes. Particle number emission indices (EIs) deduced from the observations in aged plumes are in the same range as values reported from engine certifications. This finding, together with the observed external mixing state inside the plumes, indicates that the aviation exhaust aerosol almost remains in its emission state during plume expansion. It also reveals that the particle number EIs used in global models are within the range of the EIs measured in aged plumes.

Rearrangement and expression of the antigen receptor alpha, beta and gamma genes in suppressor antigen-specific T cell lines

The rearrangement and transcription of the antigen receptor alpha, beta and gamma genes were investigated in murine antigen-specific suppressor T cell lines, to establish whether the suppressor T cell subset expresses the same antigen receptor transcripts previously found in helper and cytotoxic T lymphocytes. The genomic organization of the alpha, beta and gamma chain loci was investigated using probes representative of the entire gene or fragments from variable, joining and constant regions. The present results show that in functional suppressor T cells the three antigen receptor genes are all rearranged. The beta gene is expressed in all the tested cell lines, while the expression of the alpha and gamma genes is variable. In one cell line (LH8) alpha and gamma genes are not efficiently transcribed; in the other cell line (LA41) the gamma mRNA is found in amounts similar to beta mRNA, whereas the alpha gene is expressed at low levels. These data suggest that in suppressor T cells no direct correlation exists between the expression of alpha, beta and gamma antigen receptor genes and the effector function.

Activation of the M-CSF gene in mouse macrophages immortalized by retroviruses carrying a v-myc oncogene

We have recently immortalized murine brain macrophages (microglial cells) with a complex of retroviruses (3RV) transducing separately the myc and mil oncogenes. Surprisingly, the immortalized cells harboured an exogenous v-myc oncogene, but no v-mil sequences. The transformed macrophage cell lines grew in vitro without the addition of exogenous growth factors and were also able to grow in vivo in nude mice. In addition, they released oncogenic retroviruses able to immortalize mouse macrophages from primary splenic or thymic cultures. Molecular cloning of the provirus (VN-11) harboured in a microglial clone demonstrated that no cell-derived sequences apart from an avian v-myc gene were transduced by the recombinant retrovirus. When cells were tested for production of myeloid growth factors, they were found to transcribe and synthesize the Macrophage-Colony Stimulating Factor (M-CSF). The correlation between viral infection and activation of the M-CSF gene was tested using a M-CSF dependent cell line from which growth factor independent clones could be readily obtained after infection. The synthesis of M-CSF was detected only in cells expressing the avian v-myc protein. These data support the hypothesis that, in our conditions, macrophages can be immortalized by the expression of v-myc and the concomitant establishment of an autocrine loop triggered by viral infection.

Stimulation of in vitro rat hepatocyte proliferation by conditioned medium obtained from an immortalized macrophage cell line

The hepatomitogenic effect of conditioned medium (CDM), obtained from the N-11 mouse macrophage cell line was analysed in rat hepatocyte primary cultures. CDM concentrations from 0.01% to 100% were used and the stimulating action in terms of mitotic index (MI) was evaluated. A clear mitogenic effect was observed only with concentrations higher than 10% with peak effects around 60%. Further increase in CDM concentrations resulted in an MI decrease, and at 100% CDM the effect was totally abolished. Tests addressed to identify the presence of hepatocyte growth factor (HGF) yielded negative results. In order to identify the mitogenic factor(s) involved, we tested CDM obtained after lipopolysaccharide (LPS) stimulation of N-11 cells. Comparison of the results obtained with untreated or LPS stimulated CDMs suggested that macrophage activation does not affect the release of hepatomitogenic activity. To further characterize this macrophage-derived activity, we checked whether CDM could interact with the mitogenic effects of epidermal growth factor (EGF). CDM (10 or 50%) showed no stimulatory effect to hepatocytes cultured in the presence of a maximally stimulatory concentration of EGF. Conversely, both CDM concentrations were able to increase the MI of hepatocyte cultures treated with a suboptimal dose of EGF. These results suggest that macrophages release factor(s) which interact, in hepatocytes, with the EGF signal transduction mechanisms, or with the EGF receptor itself.

Activity-dependent dendritic targeting of BDNF and TrkB mRNAs in hippocampal neurons

The mechanisms underlying the subcellular localization of neurotrophins and their receptors are poorly understood. We show that in cultured hippocampal neurons, the mRNAs for BDNF and TrkB have a somatodendritic localization, and we quantify the extent of their dendritic mRNA localization. In the dendrites the labeling covers on average the proximal 30% of the total dendritic length. On high potassium depolarization, the labeling of BDNF and TrkB mRNA extends on average to 68% of the dendritic length. This increase does not depend on new RNA synthesis, is inhibited by the Na+ channel blocker tetrodotoxin, and involves the activation of glutamate receptors. Extracellular Ca2+, partly flowing through L-type Ca2+ channels, is absolutely required for this process to occur. At the protein level, a brief stimulation of hippocampal neurons with 10 mM KCl leads to a marked increase of BDNF and TrkB immunofluorescence density in the distal portion of dendrites, which also occurs, even if at lower levels, when transport is inhibited by nocodazole. The protein synthesis inhibitor cycloheximide abolishes this increase. The activity-dependent modulation of mRNA targeting and protein accumulation in the dendrites may provide a mechanism for achieving a selective local regulation of the activity of neurotrophins and their receptors, close to their sites of action.

Modulation of cytokine expression by cAMP analogs in myc-immortalized microglial cell lines

Expression of cytokines can be modulated by cAMP in macrophages or in primary microglial cultures. Similar to what is observed in normal conditions, treatment of immortal microglial cell lines with dibutyryl-cAMP blocked the accumulation of TNF alpha transcripts induced by lipopolysaccharide, whereas activation of Interleukin-1 alpha (IL-1 alpha) remained unaffected. Immortalized cell lines can therefore be regarded as a valid model to test the immune responsiveness of microglial cells in the presence of neuro-endocrine agents modulating cAMP levels.

Functional blockade of tyrosine kinase A in the rat basal forebrain by a novel antagonistic anti-receptor monoclonal antibody

We have exploited a new monoclonal antibody against the tyrosine kinase A (TrkA) nerve growth factor (NGF) receptor to block the NGF-TrkA interaction in the rat basal forebrain. The monoclonal antibody MNAC13 is a potent antagonist that prevents the binding of NGF to TrkA in a variety of systems. This antibody was used to study the maintenance of the cholinergic phenotype in the rat basal forebrain in vivo, by the implant of antibody-secreting cells. Basal forebrain cholinergic neurons (BFCNs) are greatly affected by the antibody treatment, both in terms of cell number and of cell soma size. When antibody-secreting cells are implanted at postnatal day 2 (P2), the effects observed at P8 are as severe as those obtained with anti-NGF antibodies and, interestingly, are observed also if anti-TrkA cells are implanted at P8, when anti-NGF antibodies, delivered by the same route, are no longer effective (). The effects induced by anti-TrkA, as those induced by anti-NGF, are reversible, but the time required for recovery and the critical period in the sensitivity of BFCNs to the functional inactivation of TrkA is twice as long than that observed when NGF is intercepted. These results demonstrate that BFCNs are more sensitive to the block of TrkA activation than they are to the block of NGF. The cloning of MNAC13 variable regions and their assembly into a functional polypeptide of reduced size (single chain Fv fragment) will allow its use in gene transfer applications.

Response to STI571 in chronic myelomonocytic leukemia with platelet derived growth factor beta receptor involvement: a new case report

Based on its ability to inhibit the tyrosine kinase activity of ABL, as well as the c-kit and the Platelet Derived Growth Factor Receptor tyrosine kinases, the spectrum of diseases that may respond to STI571 is increasing. A recently recognized subgroup of myeloproliferative disorders/myelodysplastic syndromes (MPD/MDS) has a t(5;12)(q33;p13) with the activation of the gene for PDGFBR which encodes a receptor tyrosine kinase. Here, we present the case of a patient, with MPD/MDS, and eosinophilia, carrying a translocation t(5;12)(q33;p13) who achieved a complete remission following treatment with STI571, 400 mg daily. At the time of writing he still remains in complete remission with an excellent performance status. There is clearly a need for further studies of STI 571in MPD/MDS with chromosomal translocations involving PDGFBR to confirm this promising initial result.

Subcellular localisation of neurotrophins and neurotrophin receptors: implications for synaptic plasticity

A growing body of recent evidence indicate that neurotrophins can act as mediators of neuronal plasticity. In the context of a more detailed, comprehensive understanding of the function of neurotrophins it is essential to characterize where neurotrophins are synthesised and stored and from where they are released. Here we present evidence that the mRNAs for NGF, trkB and BDNF but not trkA are localised in the dendrites of rat neurons, thus implying that neurotrophins and their receptors can be synthesised at locations close to their sites of function, with particular regard to the dendritic synapses. The significance of this finding and its possible implications for synaptic plasticity are discussed within the theoretical framework of the synapse-specific control of individual synapses of a given neuron.