["VigilanSeu.r.se": A new profession?] / « VigilanSeu.r.se ¼ : un nouveau métier ?

In January 2015, in accordance with decades of scientific work based on maintaining contact, was born an innovative device for suicide prevention: VigilanS. To ensure this link, the choice was made to build a team with an equal number of nurses and psychologists, all located within the medical regulation. Nowadays, they are named "VigilanSeur": an original entity that highlights the emergence of this new profession, at the crossroads of several disciplines.

Tumor necrosis factor alpha in human kidney transplant rejection--analysis by in situ hybridization.

Macrophagic infiltration and necrosis of rejected kidney transplants represent two pejorative patterns. It has been assumed that the macrophagic toxicity is mediated partly by secretion of tumor necrosis factor alpha. On the other hand, TNF is also involved in many inflammatory and immunological phenomena. We thus evaluated the expression of TNF mRNA by in situ hybridization in 6 rejected kidney transplants using a radiolabeled TNF-c DNA probe. Then the synthesis of TNF alpha protein was studied by immunohistochemistry using an anti-TNF alpha antibody. In severely rejected kidney grafts, TNF mRNA is expressed in some monomorphic infiltrating cells, mostly located in the deepest part of the cortex and around the tubes. These cells do not bind other probes, such as dopa-decarboxylase DNA or preproenkephalin RNA. They are also recognized by a monoclonal antibody directed against TNF alpha. What is more, this antibody binds with some glomerular endothelial and tubular epithelial cells that do not express TNF mRNA. These cells are likely target cells for TNF. In the normal kidney, there are no cells expressing TNF-alpha mRNA.

Protective effect of bone marrow and spleen suspensions on radiation-induced leukemogenesis in C57BL/6 mice.

The present experiments are an attempt to precise the type and localization of the cells involved in the protective effect of hemopoietic suspensions against the radiation-induced thymic lymphosarcoma (TLS) of C57BL/6 mice. Inocula containing variable numbers of BM or spleen CFUs from 60-day-old and 360-day-old donors were tested. According to their origin, the suspensions differed with respect to the CFU replication rate, the CFU ability to differentiate towards the T lineage and the content of the suspensions in thymic precursors. Two levels of inhibition were observed: BM suspensions from 60-day-old donors containing 1,500 CFUs had the best protective effect: 14.5% of TLS; 1,500 CFUs from 360-day-old donors were slightly but not significantly less efficient (28.5%). The second level of inhibition (36-46% of TLS) was obtained with all the following inocula: a) 1,200 and 300 spleen CFUs or 300 and 95 BM CFUs from 60-day-old donors, b) 1,500 spleen CFUs from aged donors. Seventy-six spleen CFUs from 60-day-old donors, 120 BM or 175 spleen CFUs from aged donors had no effect. These results suggest that in addition to the high replication rate of the BM CFUs as compared with spleen CFUs, cells endowed with an optimal protective effect are present in BM suspensions and are either absent or present in very small amount in spleen suspensions. These cells which induce an early repopulation of the thymus might correspond to thymic precursors.

Bovine lymphosarcoma: processing of bovine leukaemia virus-coded proteins.

This report describes pulse-chase experiments performed with cells infected with tumour-derived bovine leukaemia virus (BLV) and using purified gamma-globulins directed against BLV structural proteins, namely gp51, p24, p15 and p12. A gpr72 was found to be the precursor of the gp51 with a gpr70 intermediate. The p12 was shown to be derived from a pr40 with numerous intermediates (pr35, pr22, pr16 and pr14). The p24 and p15 originate from a pr42. Both the pr42 and pr40 are derived from a common pr70. A P45, a P52 and a P27 were also detected. Because these three proteins were found to accumulate progressively in cells and because they were not observed to be processed, they might play a physiological role in infected cells.

Distribution of terminal deoxynucleotidyl transferase activity between peaks I and II in host and donor thymic cells of bone-marrow-restored mice after X-irradiation.

The terminal deoxynucleotidyl transferase (TdT) activity and its distribution between peaks I and II after chromatographic elution were studied on days 15 and 17 after X-irradiation, in host- and donor-derived thymic cells of lethally irradiated (9 Gy) mice restored with BM cells. It was found that the population derived from the surviving host thymocytes differed markedly from the donor-derived population. The cells of host origin has a low TdT activity especially in peak II and the ratio peak I/peak II remained close to 1 instead of 0.1 in controls. These alterations reflect a reduced replication rate and possibly a modification of the cellular metabolic activity (phosphorylation-dephosphorylation). In contrast, the donor-derived elements displayed a very high TdT activity related to their elevated rate of replication, and the ratio peak I/peak II which was close to 1 on day 15 returned rapidly to normal. The impaired replication ability and the metabolic alteration of the host cells might be attributed either to a specific property of the radiation-resistant thymocytes or to residual cellular injury or to a combination of both.

Bovine lymphosarcoma: expression of BLV-related proteins in cultured cells.

Bovine leukaemia virus (BLV) is known to be the aetiological agent of enzootic bovine lymphosarcoma. As the mechanism of tumour induction is unknown, we analysed the viral proteins expressed in cultured bovine cells of different origin, i.e. from enzootic or sporadic tumourous tissues, normal cells infected or not with BLV, and the reference FLK-BLV cells. We also investigated BLVs of different origins. As well as the previously described BLV polyproteins in FLK-BLV cells (pr70 and pr45) we have also found two additional polyproteins, p52 and p27. In these four proteins we observed the combined antigenicities of p24, p15 and p12. We observed an additional polyprotein in p42, with the antigenicities of the p24 and the p15 in cells derived from tumour tissue or infected in vitro with naturally occurring BLV isolates. None of these BLV-coded proteins, nor others with cross-reacting antigenicities, were encountered in non-BLV-producing cultured cells from enzootic or sporadic tumours. The use of autologous sera did not permit the detection of any proteins in addition to the above gag-coded and env-coded proteins. Thus, there is no evidence for the existence of a gag-x fusion protein which could play a role in BLV-induced tumourigenicity.

Terminal deoxynucleotidyl transferase activity in the regenerating thymus of x-irradiated mice.

The distribution of terminal deoxynucleotidyl transferase (TdT) enzyme activity (EU per 10 8 cells) between peaks I and II was followed for a period of 42 days in regenerating thymus of lethally irradiated (9 Gy) C3H mice restored with 10 6 (C3H x AKR) F1 bone marrow cells. The detection of Thy-1.1 and Thy-1.2 surface antigens allowed for the discrimination between host and donor cells, and the main subpopulations of thymic cells were characterized by their sensitivity to H-2 k antiserum and to dexamethazone. Two peaks of TdT activity could be detected on phosphocellulose chromatographic separation. The distribution of TdT activity between these two peaks was followed during the two periods of thymic endo- and exoregeneration. Peak I TdT activity was closely correlated with the variation in the percentage of high H-2 population. Peak II activity was mostly related to low H-2 cells. The per cell content of both peak I and peak II activities exceeded the norm in rapidly expanding populations. Finally between days 10 and 14 the TdT activity of the endoregenerating population was apparently not different from that of the exoregenerating population between days 14 and 22.

Mechanism of early and late polykaryocytosis induced by the bovine leukaemia virus.

Syncytia formation induced by the bovine leukaemia virus (BLV) has been classified as 'early' or 'late' polykaryocytosis. Early polykaryocytosis arises in the first 24 h in mixed cultures of BLV-infected cells with indicator cells. Late polykaryocytosis is observed 4 to 8 days after infection of sensitive cells with cell-free infectious BLV. Our results demonstrate that the two phenomena proceed from different mechanisms. Late polykaryocytosis results from an active process dependent on the integrity of the virus genome. In contrast, early polykaryocytosis is a passive process which does not require any de novo virus synthesis but is dependent on the presence of virus proteins in inducer cells.

Establishment and propagation of a bovine leukaemia virus-producing cell line derived from the leukocyte of a leukaemic cow.

A cell line (LB59Ly) derived from the leukocytes of a leukaemic cow was established as a monolayer, which spontaneously released large amounts of a retrovirus. This virus was found to be indistinguishable from the bovine leukaemia virus (BLV) produced by the commonly used high-producing heterologous cell line (FLK-BLV). Like the latter, its reverse transcriptase activity was greater in the presence of Mg2+ cations than in the presence of Mn2+ cations; its polyacrylamide gel electrophoresis pattern showed the presence of gp51, p24, p15, p12 and p10, and the antigenicity of the two major proteins completely cross-reacted with those of BLV from FLK-BLV cells. The virus was infectious and induced early and late polykaryocytosis, the specificity of which was demonstrated by use of specific anti-BLV sera.

In vitro production and titration assays of B-tropic retroviruses isolated from C57BL mouse tumors induced by radiation leukemia virus (RadLV-Rs): effect of dexamethasone.

The effect of dexamethasone (DXM) on the replication and titration assays of B-ecotropic radiation leukemia virus (RadLV-Rs) isolates was examined. The drug was shown to enhance in vitro virus release by otherwise low producer permissive cells. DXM also stimulated infectivity and focus formation in murine S+L--permissive cells and shortened the time-appearance of virus-induced foci. In contrast to foci observed in nontreated cultures, which are generally abortive and composed of only a few morphologically transformed cells, those obtained with DXM were comparable to those induced by ecotropic retroviruses with a potent helper activity for murine sarcoma virus. In addition, DXM increased virus-induced XC cell fusion. These fundamental data allowed a more abundant in vitro production of the B-ecotropic RadLV-Rs virus isolates as well as precise infectivity titration assays.

Characterization by molecular hybridization of two viral populations derived from a radiation leukemia virus.

Two leukemogenic viral populations were derived from a radiation leukemia virus of the C57BL mouse. One (FB), in which only B-tropic virus could be detected, was obtained in vivo by serial passage of cell-free extract in newborn rats. The second (3C), a complex containing at least B-tropic and xenotropic viruses, was produced in vitro by a permanent cell line (13-3C) established from the spleen of a virus-infected C57BL mouse. In molecular hybridization experiments, the 70S RNA of Gross leukemia virus hybridized 96 and 78% of FB and 3C radioactive complementary DNA's, respectively, with a relatively high thermal stability of the duplexes formed. In contrast, the 70S RNA of Rauscher leukemia virus hybridized 23 and 20% of the FB and 3C DNA probes, respectively, with a low thermal stability. The rat-grown FB virions exhibited 50% genome homology with the viruses produced in vitro on the 13-3C cells. Finally, hybridizing the FB and 3C probes with normal or leukemic mouse spleen DNA's resulted in 89 to 100% homology. The rat-grown virions did not appear to contain detectable rat cellular DNA sequences, while about 20 complete copies of their nucleotide sequences were detected in covalent linkage with FB-infected rat spleen DNA. These findings strongly support the endogenous murine origin of the investigated virions.

Immunological nature of the inhibition of BLV-induced early polykaryocytosis by bovine sera.

A quantitative in vitro assay (EPI) was developed for the serological detection of bovine leukemia virus (BLV) infection in cattle. Positive sera inhibit early polykaryocytosis (EP) induced by BLV. We report herein experiments which demonstrate that BLV-induced antibodies are responsible for this inhibition. Serum fractionation by gel filtration and affinity chromatography indicate that EP-inhibiting activity is mediated only by immunoglobulins of the IgG class. Furthermore, on the basis of their ion-exchange chromatographic behaviour, these antibodies were classified as IgG1. We also ruled out the participation in the EP inhibition reaction of the other compounds such as polypeptides, including serum complement and interferon or DNA and RNA. These results demonstrate that EP inhibition by bovine sera is specific to BLV-induced antibodies.

Bovine leukemia virus (BLV) specific RNA in infected cells.

BLV specific RNA sequences were detected by hybridization to the single stranded DNA copy of the viral RNA in fetal lamb kidney cells infected with bovine leukemia virus (FLK-BLV). The DNA synthesis was carried out in vitro by an endogenous reaction. It was found that uninfected lamb cells do not contain RNA sequences related to the BLV genome, whereas BLV-DNA completely annealed to FLK-BLV RNAs. RNA from FLK-BLV cells contains three species of virus specific RNA which sediment respectively at 35 S, 20--24 S and 12--4 S. In view of their EDTA-sensitive association with ribosomes, viral specific RNA sequences are viral messenger RNAs and their polarity is identical to that of the 70 S viral RNA.

Characterization of antibodies responsible for the inhibition of BLV induced early polycaryoxytosis.

A quantitative in vitro assay (EPI) was developed for the serological detection of bovine leukemia virus (BLV) infection in cattle. Positive sera react in inhibiting early polycaryocytosis (EP) induced by BLV. We report here experiments which demonstrate that BLV induced antibodies are responsible for this inhibition. Serum fractionation by gel filtration and affinity chromatography indicates that EP inhibiting activity is mediated by immunoglobulins of the IgG class but not by those of the IgM or other classes. Furthermore, in view of their ion-exchange chromatographic behaviour, these antibodies were attributed to the IgG1 subclass. We also ruled out the participation in the EP inhibition rection of the other compounds like polypeptides, including serum complement and interferon or DNA and RNA. These results demonstrate that EP inhibition by bovine sera is specific of BLV induced antibodies.

Early polykaryocytosis inhibition test: evaluation of its performance in a seroepidemiological survey of bovine leukemia virus induced antibodies in cattle.

We report the results of a seroepidemiological survey, using the recently described early polykaryocytosis inhibition (EPI) assay to detect bovine leukemia virus (BLV) infection in cattle. At the herd level, there is a good correlation between epidemiological, hematological, anatomopathological data and of both the presence and titer of EP inhibiting antibodies. The EPI procedure revealed to be more sensitive than two other routine serological techniques, complement fixation and immunodiffusion. In addition, at the individual level the average EPI titers of the sera increase progressively from normal to hematologically-suspect, -- positive and finally to lymphosarcomatous animals; when the age is considered, there is a very significant increase of the amount of EP inhibiting antibodies among lymphocytotic animals, while there is only a very moderate increase of the EPI titer among hematologically normal contact animals. This suggests a loss of control of BLV expression in most lymphocytotic animals and may explain the more frequent occurrence of lymphosarcomas in this category of animals. The horizontal transmission of BLV throughout the entire life span is supported by the observation of an increase with age of the percentage of animals with EP inhibiting antibodies.