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Background. Acute psychiatric provision in the UK today as well as globally has many critics including service users and nurses. Method. Four focus groups, each meeting twice, were held separately for service users and nurses. The analysis was not purely inductive but driven by concerns with the social position of marginalised groups - both patients and staff. Results. The main themes were nurse/patient interaction and coercion. Service users and nurses conceptualised these differently. Service users found nurses inaccessible and uncaring, whereas nurses also felt powerless because their working life was dominated by administration. Nurses saw coercive situations as a reasonable response to factors 'internal' to the patient whereas for service users they were driven to extreme behaviour by the environment of the ward and coercive interventions were unnecessary and heavy handed. Conclusion. This study sheds new light on living and working in acute mental health settings today by comparing the perceptions of service users and nurses and deploying service user and nurse researchers. The intention is to promote better practice by providing a window on the perceptions of both groups.
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ACCESSIBLE SUMMARY: Accelerated mental health nurse training attracts talented graduates, many with a psychology degree. Our study shows that such trainees feel incompatible with the nursing culture. Consequently, professional identification is inhibited, and on qualifying these nurses may choose to develop their careers elsewhere. Nurse educators and mentors should pay greater attention to nurturing a positive professional identity in trainees. Alongside their attainment of knowledge and skills, nursing trainees are moulded by a professional culture and inculcated to norms of beliefs and behaviour. The process of professional identification may be inhibited by accelerated nurse training and an influx of psychology graduates potentially using mental health nursing qualification as a springboard to other career opportunities. This study explored facilitators and barriers to professional identification in newly qualified nurses of accelerated postgraduate training. Qualitative interviews were conducted with 10 nurses who had recently completed a postgraduate diploma in mental health nursing at King's College London. Participants identified more with the mental health field than with the broader profession of nursing. They defined their practice in terms of values rather than skills and found difficulty in articulating a distinct role for mental health nursing. Although participants had found experience in training and as a registered practitioner rewarding, they were concerned that nursing may not fulfil their aspirations. Professional identity is likely to be a major factor in satisfaction and retention of nurses. Training and continuing professional development should promote career advancement within clinical nursing practice.
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Educação de Pós-Graduação em Enfermagem/normas , Satisfação no Emprego , Papel do Profissional de Enfermagem/psicologia , Enfermagem Psiquiátrica/normas , Adulto , Feminino , Humanos , MasculinoRESUMO
BACKGROUND: The impact of staff perceptions of daily work pressures on burnout requires further exploration because both issues may be adversely affecting the quality of staff interactions with service users. OBJECTIVES: To use a model of 'stakeholder involvement' to develop and test a self-report instrument capturing nursing staff perceptions of the daily pressures of working in acute in-patient mental health wards. DESIGN: Measure development followed a participatory methodology, followed by psychometric testing of the new measure of the daily pressures of working on an acute ward (VOTE). SETTINGS: Acute in-patient wards in an inner London mental health trust. PARTICIPANTS: All nursing staff from acute in-patient settings are eligible for this study. In total 376 staff (qualified nurses and healthcare assistants) were involved at the various stages of measure development and testing. METHODS: Focus groups of nursing staff met to discuss their perceptions of acute wards. A twenty item measure was generated through thematic analysis of these data and staff feedback. Reliability and validity were tested and the effects of demographic characteristics on VOTE, and VOTE on burnout were examined. RESULTS: Staff found VOTE easy to understand and complete. Test-retest reliability and the internal consistency of the measure and subscales were good. A test of criterion validity showed that staff with negative perceptions of the daily pressures of the working on an acute ward also had negative perceptions of job satisfaction and high levels of burnout. Regression modelling showed that VOTE had a significant effect on burnout. CONCLUSIONS: VOTE is a concise measure which combines aspects of care provision as well as the organisational and professional stressors of acute ward working. VOTE can be used to further explore how staff perceptions of the daily pressures of acute ward working affect the quality of care delivered.
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Atitude do Pessoal de Saúde , Pacientes Internados , Recursos Humanos de Enfermagem Hospitalar/psicologia , Esgotamento Profissional , Humanos , Londres , Psicometria , Reino UnidoRESUMO
Violence and aggression is acknowledged as a serious issue in the mental health services. The aims are to explore whether de-escalation and physical intervention training is effective in reducing incidents and incident severity on a Psychiatric Intensive Care Unit (PICU) and to consider the cost impact. Poisson regression analysis was used to compare the number and severity of incidents on a PICU before and after de-escalation and restraint training. This study shows no significant differences in the number or severity of incidents before and after training. Objective assessment in the evaluation of interventions to improve the safety of the inpatient services is difficult when data is recorded inconsistently or inaccurately. The severity of incidents needs to be defined more fully to allow accurate measurement of the efficiency of techniques employed to resolve violence. The cost impact of training in the management of violence in relation to the benefits remains unclear in the absence of accurate data being recorded.
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Agressão/psicologia , Restrição Física/métodos , Ensino/métodos , Violência/prevenção & controle , Adulto , Feminino , Humanos , Masculino , Serviços de Saúde Mental/normasRESUMO
There is a growing body of evidence looking at the effects of cannabis use on those with schizophrenia with concerning results. This has led to the development of a number of interventions that are intended to improve outcomes for this client group. However, the methodological quality of some dual diagnosis research has been questioned in reviews for using outcome measures that are not tested as reliable and valid in the population for which they are intended for use. This literature review assesses the self-report measures that have been reliability and validity tested in populations of people with schizophrenia who use cannabis and reports on their appropriateness for use in further research studies. An overview of the most appropriate biochemical tests for cannabis is also given.
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Pacientes Internados , Abuso de Maconha/prevenção & controle , Pesquisa em Enfermagem/normas , Esquizofrenia/enfermagem , Redução do Dano , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Reprodutibilidade dos Testes , Comportamento de Redução do Risco , Esquizofrenia/complicações , Esquizofrenia/terapiaRESUMO
Current policy from the Department of Health advocates for an integrated approach to treating patients with a dual diagnosis. However, pragmatic and clinically effective brief interventions that can be delivered by nurses across mental health settings remain underdeveloped. Motivational interviewing has had some successful exposure in the field of dual diagnosis; however, harm reduction remains unexplored both conceptually and in terms of clinical intervention. This literature review examines the notion of harm reduction as a method of identifying and reducing the harm associated with the misuse of drugs and alcohol in relation to mental health problems. Currently there is a paucity of good quality evidence for integrated interventions in the treatment of dually diagnosed patients. Therefore, the papers are analysed in respect of their methodological quality and contribution to the evidence base to inform both future research and mental health nursing practice.
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Diagnóstico Duplo (Psiquiatria)/enfermagem , Redução do Dano , Entrevista Psicológica , Psicoterapia Breve/métodos , Medicina Baseada em Evidências , Humanos , Projetos de PesquisaRESUMO
Within the framework of a research project investigating methods to decrease mastitis incidence, farmer groups for participatory training in a modified Farmer Field School approach were initiated in order to improve animal health and farmer knowledge in mastitis control technologies in smallholder dairy farms in the Jinja district of Uganda. Two peri-urban groups and one rural group met for common learning and training two hours per fortnight during a 12-month period, facilitated by two local extension agents together with one or two scientists from Makerere University. Farmers rotated each time between farms owned by group participants, which demanded mutual trust, openness and respect. From their own assessment the farmers felt they had improved their milk production and reduced mastitis incidence on their farms. In an evaluation workshop, they articulated how they had built up common knowledge and experience from training in systematic clinical examination of animals, evaluation of the farm environments, and identification of improvements. Much of the acquired new knowledge was about basic dairy cow management and husbandry practices. In addition, they gave examples of how they were now used as resource persons in their local communities. Principles of learning and empowerment are discussed.
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Agricultura/educação , Criação de Animais Domésticos/educação , Indústria de Laticínios/educação , Animais , Bovinos , Estudos Transversais , Educação , Feminino , Humanos , Masculino , Mastite Bovina/prevenção & controle , População Rural , População Suburbana , UgandaRESUMO
Retroviral insertional mutagenesis has proven to be a powerful in vivo approach for identifying genetic mutations involved in tumorigenesis or developmental abnormalities. Applying this approach to an in vitro system, where experimental design can be readily manipulated, would greatly increase its efficacy. In this study, we sought to determine whether retroviral insertional mutagenesis could be used to isolate cell mutants, in which the transcriptional activation of a receptor gene has occurred. Cells of the myeloid progenitor cell line FDC-P1(M), which do not express the alpha receptor subunit (GMRalpha) for granulocyte-macrophage colony-stimulating factor (GM-CSF), were infected and selected for growth in GM-CSF. Over 100 mutants were isolated at a frequency up to ninefold higher than that of uninfected controls. Expression of GMRalpha in these mutants was confirmed by blocking proliferation with GM-CSF antibodies, detection of high-affinity receptors, and Northern blot analysis. Significantly, in 7/18 mutants analyzed, gross DNA rearrangements had occurred in the GMRalpha locus. These rearrangements were demonstrated to be due to intergenic rearrangements, juxtaposing an active enhancer/promoter upstream of the GMRalpha gene. In one mutant it could be demonstrated that the wild-type allele was also expressed, providing evidence that secondary mutations had occurred. The implications of these results for retroviral insertional mutagenesis are discussed.
Assuntos
Vetores Genéticos , Mutagênese Insercional/fisiologia , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos/genética , Retroviridae/genética , Ativação Transcricional/fisiologia , Animais , Anticorpos/farmacologia , Divisão Celular/fisiologia , Linhagem Celular , Clonagem Molecular , Expressão Gênica/fisiologia , Rearranjo Gênico/fisiologia , Células-Tronco Hematopoéticas/citologia , Íntrons/genética , Testes de Neutralização , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos/imunologia , Proteínas Recombinantes de Fusão/genéticaRESUMO
We show a dramatic downregulation of the stem cell factor (SCF) receptor in different hematopoietic cell lines by murine stroma. Growth of the human erythroid/macrophage progenitor cell line TF-1 is dependent on granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3). However, TF-1 cells clone and proliferate equally well on stroma. Independent stroma-dependent TF-1 clones (TF-1S) were generated on MS-5 stroma. Growth of TF-1S and TF-1 cells on stroma still requires interaction between c-kit (SCF receptor) and its ligand SCF, because antibodies against c-kit inhibit growth to less than 2%. Surprisingly, c-kit receptor expression (RNA and protein) was downregulated by 2 to 3 orders of magnitude in TF-1S and TF-1 cells grown on stroma. This stroma-dependent regulation of the kit receptor in TF-1 was also observed on exposure to kit ligand-negative stroma, thus indicating the need for heterologous receptor ligand interaction. Removal of stroma induced upregulation by 2 to 4 orders of magnitude. Downregulation and upregulation of c-kit expression could also be shown for the megakaryocytic progenitor cell line M-07e and was comparable to that of TF-1, indicating that stroma-dependent regulation of c-kit is a general mechanism. Downregulation may be an economic way to compensate for the increased sensitivity of the c-kit/ligand interaction on stroma. The stroma-dependent c-kit regulation most likely occurs at the transcriptional level, because mechanisms, such as splicing, attenuation, differential promoter usage, or mRNA stability, could be excluded.
Assuntos
Regulação para Baixo , Regulação da Expressão Gênica , Células-Tronco Hematopoéticas/metabolismo , Proteínas Proto-Oncogênicas c-kit/genética , Células Estromais/fisiologia , Animais , Sequência de Bases , Northern Blotting , Divisão Celular , Linhagem Celular , Fator Estimulador de Colônias de Granulócitos e Macrófagos/farmacologia , Humanos , Interleucina-3/farmacologia , Camundongos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Proteínas Proto-Oncogênicas c-kit/metabolismo , RNA Mensageiro/metabolismo , Proteínas Recombinantes , Fator de Células-Tronco/metabolismo , Transcrição GênicaRESUMO
The use of retroviral vectors for gene transfer into animals has been severely hampered by the lack of provirus transcription in the early embryo and embryonic stem (ES) cells. This primary block in provirus expression is maintained in differentiated cells by a cis-acting mechanism that is not well characterized. Retroviral vectors based on the murine embryonal stem cell virus (MESV), which overcome the transcriptional block in ES cells, were constructed to investigate this secondary mechanism. These vectors transferred G418 resistance to ES cells with the same efficiency as to fibroblasts, but overall transcript levels were greatly reduced. A mosaic but stable expression pattern was observed when single cells from G418-resistant clones were replated in G418 or assayed for expression of LacZ or interleukin-3. The expression levels in independent clones were variable and correlated inversely with methylation. However, a second, more pronounced, block to transcription was found upon differentiation induction. Differentiation of the infected ES cells to cells permissive for retroviral expression resulted in repression and complete extinction of provirus expression. Extinction was not accompanied by increased levels of methylation. Provirus expression is thus regulated by two independent cis-acting mechanisms: (i) partial repression in the undifferentiated state, accompanied by increased methylation but compatible with long-term, low expression of retroviral genes, and (ii) total repression and extinction during early stages of differentiation, apparently independent of changes in methylation. These results indicate a time window early during the transition from an undifferentiated to a differentiated stage in which provirus expression is silenced. The mechanisms are presently unknown, but elucidation of these events will have an important impact on vector development for targeting stem cells and for gene therapy.
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Vetores Genéticos , Retroviridae/genética , Animais , Sequência de Bases , Diferenciação Celular , Células Cultivadas , Metilação de DNA , DNA Viral/química , DNA Viral/genética , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Transferência de Genes , Genes Virais , Camundongos , Mosaicismo , Mutação , Regiões Promotoras Genéticas , Provírus/genética , Células-Tronco/citologia , Células-Tronco/metabolismo , Células-Tronco/virologiaRESUMO
A coculture system of a murine erythroblastic leukemia cell line (ELM-D) with its supportive stromal cell line (MS-5) was established. Long-term growth of ELM-D cells is strictly stroma cell dependent. Interaction between stem cell factor (SCF) and its receptor, c-kit, was demonstrated to be important for stroma cell-dependent growth by anti c-kit neutralizing monoclonal antibody (mAb) inhibition experiments. Significantly, soluble growth factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) or SCF of MS-5 stromal cells (MS-5 CM) could replace the requirement of stroma cells for a considerable period. However, ELM-D cells maintained in these growth factors underwent clonal extinction after 3-6 weeks unless contact with stroma was re-established. Furthermore, IL-3 or GM-CSF acted in a dominant manner in inducing cell death in the presence of stroma cells. Cells showing clonal extinction undergo programmed cell death and do not differentiate. These altered growth properties of ELM-D cells exposed to soluble growth factors or to stroma cells appear to be analogous to those described for T or B cells primed by antigen presenting cells and then grown in growth factors.
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Substâncias de Crescimento/fisiologia , Leucemia Eritroblástica Aguda/patologia , Animais , Divisão Celular/efeitos dos fármacos , Células Clonais , Meios de Cultura , Fator Estimulador de Colônias de Granulócitos e Macrófagos/farmacologia , Interleucina-3/farmacologia , Camundongos , Proteínas Proto-Oncogênicas c-kit/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-kit/metabolismo , RNA Mensageiro/metabolismo , Solubilidade , Células Estromais/patologiaRESUMO
The polycythemic strain of the spleen focus-forming virus (SFFVp) contains the most potent murine retroviral enhancer configuration known so far for gene expression in myeloerythroid hematopoietic cells. In the present study, we mapped two crucial elements responsible for the high activity of the SFFVp enhancer to an altered upstream control region (UCR) containing a GC-rich motif (5'-GGGCGGG-3') and to a unique enhancer core (5'-TGCGGTC-3'). Acquisition of these motifs accounts for half of the activity of the complete retroviral enhancer in hematopoietic cells, irrespective of the developmental stage or lineage. Furthermore, the UCR motif contains the major determinant for the enhancer activity of SFFVp in embryonic stem (ES) cells. Using electrophoretic mobility shift assays, we show that the UCR of SFFVp, but not of Friend murine leukemia virus, is targeted by the ubiquitous transcriptional activator, Sp1. The core motif of SFFVp creates a specific and high-affinity target for polyomavirus enhancer binding protein/core binding factor (PEBP/CBF) and excludes access of CAAT/enhancer binding protein. Cotransfection experiments with ES cells imply that PEBP/CBF cooperates with the neighboring element, LVb (the only conserved Ets consensus in the SFFVp enhancer), and that the Sp1 motif in the UCR stimulates transactivation through the Ets-PEBP interaction. Putative secondary structures of the retroviral enhancers are proposed based on these data.
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Proteínas de Ligação a DNA/metabolismo , Elementos Facilitadores Genéticos , Proteínas de Neoplasias , Fator de Transcrição Sp1/metabolismo , Vírus Formadores de Foco no Baço/genética , Fatores de Transcrição/metabolismo , Animais , Sequência de Bases , Sítios de Ligação , Proteínas Estimuladoras de Ligação a CCAAT , Células COS , Linhagem Celular , Fatores de Ligação ao Core , DNA Viral , Vírus da Leucemia Murina de Friend , Células-Tronco Hematopoéticas , Dados de Sequência Molecular , Vírus da Leucemia Murina de Moloney , Proteínas Nucleares/metabolismo , Conformação de Ácido Nucleico , Policitemia , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-etsRESUMO
The Friend spleen focus-forming virus induces a massive expansion of erythroid progenitor cells resulting in polycythemia and splenomegaly. The pathogenic agent is the membrane glycoprotein gp55, encoded by the env gene. Recent evidence indicates that gp55 binds to and activates the erythropoietin (Epo) receptor. It is not clear, however, whether gp55 completely mimics the natural receptor ligand (Epo). To directly compare both effectors, we constructed selectable retroviral vectors which carry either the env or the Epo gene. The selection marker allowed for clonal analysis of infected cells. After infection of DBA/2J mice, the spleen weight, hematological indices, and Epo titer of peripheral blood were monitored. Although both viruses induced an acute erythrocytosis, there were significant differences in disease phenotype and progression. The Epo virus caused an enhanced increase of hematocrit and erythrocytes, whereas with the env virus the pool of late progenitors (CFU-erythroid) was dramatically expanded, resulting in a more severe splenomegaly. The distribution of cytologically recognizable erythroid precursors was shifted towards immature cell types by the env vector compared with Epo. These data suggest that Epo and gp55 differentially affect proliferation and differentiation. Gp55 appears to promote proliferation over differentiation, whereas Epo preferentially drives differentiation.
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Eritropoetina/fisiologia , Vetores Genéticos , Policitemia/etiologia , Vírus Formadores de Foco no Baço/genética , Proteínas do Envelope Viral/fisiologia , Animais , Sequência de Bases , Células Precursoras Eritroides/fisiologia , Eritropoetina/genética , Feminino , Camundongos , Camundongos Endogâmicos DBA , Dados de Sequência Molecular , Fenótipo , Proteínas do Envelope Viral/genéticaRESUMO
Infection of sensitive adult mice with myeloproliferative sarcoma virus (MPSV) results in a myeloproliferative syndrome. Two components of the viral genome are required to induce this unique pathology: the mos oncogene and sequences within the U3 region of the long terminal repeat (LTR). In studies designed to identify the target cell of MPSV and thus better understand the mechanism by which a myeloproliferative syndrome is induced, we have infected a series of T cell lines with MPSV-based vectors. The results presented here show that infection with neoR MPSV abrogates the requirement for an antigen-specific or feeder cell-dependent stimulation, without altering the requirement for interleukin 2. Significantly, this response is not dependent on the mos oncogene, but requires sequences within the U3 region of the MPSV LTR. No alteration in the constitutive or induced levels of lymphokines released by these cells was observed. These results suggest a model in which T cells acquire a proliferative advantage by uncoupling the proliferative response from the lymphokine synthesis that is induced by activation of the T cell receptor. These cells are thus poised for antigen stimulation and secretion of cytokines that stimulate myelopoiesis.
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Transformação Celular Neoplásica , Ativação Linfocitária , Vírus do Sarcoma Murino de Moloney/genética , Receptores de Antígenos de Linfócitos T/imunologia , Vírus do Sarcoma Murino/genética , Linfócitos T/imunologia , Linhagem Celular , Fatores Estimuladores de Colônias/biossíntese , Replicação do DNA , Vetores Genéticos , Fator Estimulador de Colônias de Granulócitos e Macrófagos , Substâncias de Crescimento/biossíntese , Interleucina-2/farmacologia , Cinética , Linfocinas/biossíntese , Sequências Repetitivas de Ácido Nucleico , Linfócitos T/efeitos dos fármacosRESUMO
The malignant histiocytosis sarcoma virus (MHSV), in contrast to other viruses with the ras oncogene, induces acute histiocytosis in newborn and adult mice. Molecular structure and function studies were initiated to determine the basis of its unique macrophage-transforming potential. Characterization of the genomic structure showed that the virus evolved by recombination of the Harvey murine sarcoma virus (Ha-MuSV) and a virus of the Friend-mink cell focus-forming virus family. Structural analysis of MHSV showed two regions of the genome that are basically different from the Ha-MuSV: (i) the ras gene, which is altered by a point mutation in codon 181 leading to a Cys----Ser substitution of the p21 protein, and (ii) the U3 region of the long terminal repeat, which is largely derived from F-MCFV and contains a deletion of one direct repeat as well as a duplication of an altered enhancer-like region. Biological studies of Ha-MuSV, MHSV, and recombinants between the two viruses show that the U3 region of the MHSV long terminal repeat is essential for the malignancy and specificity of the disease. A contributing role of the ras point mutation in determining macrophage specificity, however, cannot be excluded.
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Transformação Celular Neoplásica , Vírus do Sarcoma Murino de Harvey/genética , Vírus da Leucemia Murina/genética , Vírus Indutores de Focos em Células do Vison/genética , Recombinação Genética , Sequências Repetitivas de Ácido Nucleico , Vírus do Sarcoma Murino/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Linhagem Celular , Clonagem Molecular , Códon/genética , DNA Viral/genética , Genes Virais , Genes ras , Vírus do Sarcoma Murino de Harvey/patogenicidade , Histiocitose/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Vírus Indutores de Focos em Células do Vison/patogenicidade , Dados de Sequência Molecular , Mapeamento por Restrição , Homologia de Sequência do Ácido Nucleico , Baço/microbiologia , Transfecção , Proteínas do Envelope Viral/genéticaRESUMO
At least two separate but interdependent events are required to attain autonomous growth as a consequence of ectopic expression of the multilineage colony-stimulating factor gene in hematopoietic progenitor cells. The rate at which the second event occurs is more than 3 orders of magnitude higher in precursor cell lines (FDC-P1 or FDC-P2) than in stem cell lines (FDC-Pmix). Autonomous, but not density-dependent, growth is tightly coupled to tumorigenicity in precursor cells; however, neither growth-factor-independent nor autonomously growing stem cell lines are tumorigenic.
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Transformação Celular Neoplásica , Fatores Estimuladores de Colônias/genética , Expressão Gênica , Células-Tronco Hematopoéticas/citologia , Mutação , Animais , Divisão Celular/efeitos dos fármacos , Linhagem Celular , Fatores Estimuladores de Colônias/imunologia , Fatores Estimuladores de Colônias/farmacologia , Vetores Genéticos , Células-Tronco Hematopoéticas/metabolismo , Soros Imunes , Cinética , CamundongosRESUMO
Tumorigenesis of hemopoietic cells and acquisition of factor independence as a consequence of aberrant growth factor release are closely correlated. In previous work we were able to dissect two stages leading to growth factor autonomy of cells: the first step requires the secretion of the constitutively expressed CSF gene product and extracellular interaction with its cognate receptor. This requirement for external stimulation is abrogated by a second step. We were interested in characterizing the parameters that influence the conversion from nonautonomous to autonomous growth properties of hematopoietic precursor cells. The frequency with which this alteration occurs varies and correlates with the level of growth factor production. However, a significant increase of CSF production accompanying the progression to autonomy could not be detected. We thus conclude that there is no direct link between level of CSF production and acquisition of true autonomy but an indirect influence enhancing the frequency of genetic alteration(s) that lead to growth autonomy. Lang et al. have suggested that the acquisition of autonomous growth occurs due to internal receptor-ligand interaction. Indeed, Keating and Williams have claimed that PDGF may react with an intracellular PDGF receptor resulting in autocrine stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
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Transformação Celular Neoplásica/genética , Fatores Estimuladores de Colônias/genética , Expressão Gênica/fisiologia , Células-Tronco Hematopoéticas/fisiologia , Animais , Divisão Celular , Linhagem Celular , Células Cultivadas , Vetores Genéticos/fisiologia , Retroviridae/genéticaRESUMO
It has been postulated that the disruption of the normal hormonal regulation of blood cell formation and proliferation leads to the autonomous growth of hematopoietic progenitors or stem cells and thus to leukeamia. We have utilized established hematopoietic cell lines to establish the different mechanism by which growth autonomy is acquired. The analysis of thirteen spontaneous factor-independent mutants revealed that the majority (12/13) secreted a factor that stimulated growth of the parental cell line. Thus, autocrine stimulation may be a important mechanism by which normal growth control is disrupted. This is supported by the observation of Young and Griffin (1987) that some cells isolated from patients with acute myeloblastic leukemia (AML) autogenously produce growth factor. In the majority of Dind mutants more closely examined, growth factor gene activation was due to the juxtapostion of a retrotransposon. Although the exact nature of the involvement of human retroviruses in inducing leukemia has not been elucidated, one could envisage that altered growth factor regulation due to integration of the virus may play an important role. The existence of a second class of Dind mutants that have obtained factor-independence by a mechanism not involving factor production concurs with the acquisition of factor-independent growth in hematopoietic cells after introduction of some oncogenes. Several models have been proposed to explain how oncogenes may "short circuit" and thus activate the normal signal transduction pathway by mimicking the active receptor, transducer, or effector (Weinberg, 1985). To investigate more closely the role of autocrine stimulation in the induction of growth autonomy and tumorigenicity, retroviral vectors expressing either GM-CSF or IL3 were introduced into factor-dependent hematopoitic cell lines. Non-linear clonability of infected cell lines in the absence of exogenous growth factor and inhibition of proliferation by antiserum supported a model of autocrine stimulation. However, a secondary event, correlated with amount of factor released, often occurred that abrogated the requirement for secreted CSF. Growth of cells in which this alteration had occured was cell-density independent and could not be blocked by antibody. It has been postulated that autogenous factor may react with its receptor intracellularly (Lang et al., 1985). The results presented here cannot exclude that the secondary events may allow the internal interaction of receptor and factor.(ABSTRACT TRUNCATED AT 400 WORDS)
Assuntos
Substâncias de Crescimento/genética , Sistema Hematopoético/patologia , Animais , Divisão Celular , Transformação Celular Neoplásica , Substâncias de Crescimento/farmacologia , Sistema Hematopoético/efeitos dos fármacos , Camundongos , MutaçãoRESUMO
Autocrine stimulation of cells by aberrant synthesis of growth factor may lead to malignant transformation, either as a direct consequence of endogenous factor production or as a first step of a series of successive events. Introduction of the granulocyte/macrophage colony-stimulating factor (GM-CSF) cDNA clone into a vector based on the myeloproliferative sarcoma virus allowed efficient transfer and expression of GM-CSF in factor-dependent myeloid cell lines (FDC-P1 and FDC-P2). Factor-independent growth was acquired when the vector was introduced into the GM-CSF-responsive FDC-P1 cell line but not the multi-CSF-dependent FDC-P2 line. Nonlinear clonability in the absence of exogenous growth factor and growth inhibition by GM-CSF antiserum support a model of autocrine stimulation that requires interaction of factor and receptor at the outer membrane. However, many, but not all, infected FDC-P1 cells acquired subsequently a second mutation that abrogated the requirement of GM-CSF secretion and external interaction. The nature of the second step, which presumably leads to tumorigenicity of these cells, is not well understood, but its frequency could be correlated with the level of GM-CSF released by an individual cell clone.