RESUMEN
The prevalence of antibiotic-resistant bacteria in Southeast Asia is a significant concern, yet there is limited research on the gut resistome and its correlation with lifestyle and environmental factors in the region. This study aimed to profile the gut resistome of 200 individuals in Malaysia using shotgun metagenomic sequencing and investigate its association with questionnaire data comprising demographic and lifestyle variables. A total of 1038 antibiotic resistance genes from 26 classes were detected with a mean carriage rate of 1.74 ± 1.18 gene copies per cell per person. Correlation analysis identified 14 environmental factors, including hygiene habits, health parameters, and intestinal colonization, that were significantly associated with the resistome (adjusted multivariate PERMANOVA, p < 0.05). Notably, individuals with positive yeast cultures exhibited a reduced copy number of 15 antibiotic resistance genes. Network analysis highlighted Escherichia coli as a major resistome network hub, with a positive correlation to 36 antibiotic-resistance genes. Our findings suggest that E. coli may play a pivotal role in shaping the resistome dynamics in Segamat, Malaysia, and its abundance is strongly associated with the community's health and lifestyle habits. Furthermore, the presence of yeast appears to be associated with the suppression of antibiotic-resistance genes.
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Microbioma Gastrointestinal , Microbiota , Humanos , Malasia , Escherichia coli/genética , Saccharomyces cerevisiae , Microbioma Gastrointestinal/genética , Heces/microbiología , Antibacterianos/farmacología , DemografíaRESUMEN
PURPOSE: This study aimed, firstly, to assess the determinants of return to work (RTW), secondly, to explore the amount of annual wage loss, and finally, to discover the determinants of wage loss among breast cancer (BC) survivors. METHODS: A cross-sectional study design was used in this research. The data was collected via interview using a validated questionnaire. Logistic regression models were developed to discover the significant determinants of RTW and of wage loss among BC survivors. RESULTS: A total of 256 BC survivors were included in this study. The analysis showed that there was a 21% loss of or reduction in mean income within 1 year after diagnosis. The significant predictors of RTW are being a government employee, having reduced wages or wage loss, and if the case had been diagnosed 1 year or more ago. Being a private sector employee and having a late stage of cancer was a barrier to RTW. The main risk factors for reduced wages or wage loss were belonging to the age group of 40-59 years, being of Chinese or Indian ethnicity, having low educational status, and not returning to work. However, belonging to the higher monthly income group (earning > RM 2000) is a protective factor against the risk of reduced wages or wage loss. CONCLUSIONS: Non-RTW and wage loss after diagnosis of BC may result in the survivors experiencing a significant financial burden. Assessment of these patients is becoming more crucial because more women participate in the workforce in Malaysia nowadays and because BC is managed using multiple treatment modalities with their consequences could lead to long absences from work.
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Supervivientes de Cáncer/psicología , Reinserción al Trabajo/economía , Reinserción al Trabajo/psicología , Salarios y Beneficios/economía , Adulto , Anciano , Estudios Transversales , Femenino , Humanos , Malasia , Masculino , Persona de Mediana Edad , Reinserción al Trabajo/estadística & datos numéricos , Encuestas y Cuestionarios , Adulto JovenRESUMEN
Objective: To retrospectively investigate the long-term swallowing function of patients with laryngeal carcinoma, who underwent partial laryngectomy, discuss the effectiveness and reliability of Kubota drinking test in the assessment of patients with dysphagia, who underwent partial laryngectomy, and analyze the influence of different ways of operation on swallowing function. Methods: Clinical data were retrospectively analyzed on 83 patients with laryngeal carcinoma, who underwent partial laryngectomy between September 2012 and August 2015. Questionnaire survey, Kubota drinking test and video fluoroscopic swallowing study (VFSS) were conducted for patients during a scheduled interview. Patients were grouped by two ways: the one was whether epiglottis was retained, and the other was whether either arytenoids or both were reserved. The influence of different surgical techniques on swallowing function was analyzed according to the results of Kubota drinking test. The agreement and reliability of Kubota drinking test were statistically analyzed with respect to VFSS treated as the gold standard. SPSS23.0 software was used to analyze the data. Results: Questionnaire results revealed that among 83 patients underwent partial laryngectomy 32.53% suffered from eating disorder, and 43.37% experienced painful swallowing. The incidence of dysphagia was 40.96% according to the results of Kubota drinking test. There was statistical difference between the group with epiglottis remained and that having epiglottis removed in terms of the absence of dysphagia and severity. The statistical values of normal, moderate and severe dysphagia were in the order of 18.160, 7.229, 12.344(P<0.05). Also, statistical difference existed between the groups with either and both arytenoids reserved in terms of the absence of dysphagia as well as that of intermediate severity, and their statistical values were 4.790 and 9.110(P<0.05). A certain degree of agreement and reliability was present between the results of Kubota drinking test and VFSS(Kappa=0.551, r=0.810). Conclusions: It was of considerable significance to reserve epiglottis and arytenoids for the retention of swallowing function for patients post partial laryngectomy. There are certain degree of agreement and reliability between the results of Kubota drinking test and VFSS. The test, therefore, could be used as a tool for screening patients suffering from dysphagia post partial laryngectomy.
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Trastornos de Deglución/diagnóstico , Deglución , Laringectomía/efectos adversos , Complicaciones Posoperatorias/diagnóstico , Anciano , Cartílago Aritenoides , Carcinoma/cirugía , Trastornos de Deglución/epidemiología , Trastornos de Deglución/etiología , Epiglotis , Femenino , Humanos , Incidencia , Neoplasias Laríngeas/cirugía , Laringectomía/métodos , Masculino , Persona de Mediana Edad , Complicaciones Posoperatorias/epidemiología , Reproducibilidad de los Resultados , Estudios Retrospectivos , Encuestas y CuestionariosRESUMEN
In Libya, cervical cancer is ranked third as the most frequent cancer among women with early diagnosis being shown to reduce morbidity and mortality. Health-care providers can influence women's screening behaviours, and their lack of recommendations for screening can be one of the barriers that affect women's participation in screening programmes. This study aims to assess the health-care provider's perception around cervical cancer screening. In-depth, face-to-face interviews were conducted with 16 health-care providers, from both public and private sectors in Az-Zawiya city, Libya, between February and July of 2014. The interviews were recorded and transcribed, then analysed using thematic analysis. Our findings suggest that health-care providers did not provide sufficient information regarding cervical cancer screening for women who attend health-care facilities. The results highlight the role played by health-care professionals in motivating women to attend cervical cancer screening programs, and the need for health education of health-care providers to offer a precious advice regarding the screening. On the other hand, health-care providers highlighted that implementation of reminding system of cervical cancer screening will support them to improve screening attendance. In addition, health-care providers stressed the necessity for educational and awareness campaigns of cervical cancer screening among Libyan women.
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Actitud del Personal de Salud , Detección Precoz del Cáncer/psicología , Neoplasias del Cuello Uterino/prevención & control , Publicidad , Concienciación , Costos y Análisis de Costo , Detección Precoz del Cáncer/economía , Femenino , Educación en Salud , Gastos en Salud , Conocimientos, Actitudes y Práctica en Salud , Humanos , Libia , Masculino , Motivación , Aceptación de la Atención de Salud/psicología , Aceptación de la Atención de Salud/estadística & datos numéricos , Cooperación del Paciente , Percepción , Guías de Práctica Clínica como Asunto , Sector Privado , Sector Público , Calidad de la Atención de Salud , Sistemas Recordatorios , Frotis Vaginal/economía , Frotis Vaginal/psicología , Frotis Vaginal/estadística & datos numéricosRESUMEN
OBJECTIVE: To explore the sensitivity and specificity of colposcopy directed biopsy (CDB) and the value of loop electrosurgical excision procedure (LEEP) for the diagnosis and treatment of microinvasive cervical cancer (MCC). METHODS: One hundred and thirty five patients with MCC were diagnosed with LEEP in Obstetrics and Gynecology Hospital, Fudan University from April 2008 to November 2010, and were retrospectively analyzed on CDB diagnoses and following treatment after LEEP. According to patient's desire for preservation of fertility and cone margin status, following strategies after LEEP included follow-up, second LEEP, hysterectomy, modified radical hysterectomy and radical hysterectomy. Single and multiple factors related to residual lesions after LEEP were analysed with Pearson Chi-square test and logistic regression model, respectively. RESULTS: CDB diagnosed MCC with a sensitivity of 4.4 % (6/135), specificity of 100.0% (4 680/4 680), and false negative rate of 95.6% (129/135). Among the 135 patients, 29 did not receive further treatment in our hospital and lost contact. One hundred and six patients had secondary treatment or follow-up in our hospital, 4 of among which were closely followed up; one hundred and two received further treatment, which included 6 cases with second LEEP (3 received extrafascial hysterectomy after repeat LEEP), 59 cases hysterectomy, 14 cases modified radical hysterectomy and 26 cases radical hysterectomy. For factors related to residual lesions after LEEP, single factor analysis showed that the ratio of residual lesion in patients aged 27-39, 40-49 and 50-65 years were respectively 19.0% (11/58), 15.4% (10/65) and 5/12 (χ(2)=4.505, P=0.105). Residual lesions occurred in 24.7% (23/93) of patients with positive LEEP margins, which was more than that 7.1% (3/42) of patients with negative LEEP margins (χ(2)=5.756, P=0.016). The ratio of residual lesions in patients with positive endocervical, ectocervical and deep stromal margins were respectively 29.6%(8/27), 17.1%(7/41) and 30.6%(11/36; χ(2)= 2.275, P=0.321). Residual lesions in patients with or without lymph vascular space invasion (LVSI) were 2/7 and 18.8% (24/128), respectively (χ(2)=0.412, P=0.521). The ratio of residual lesions in patients with invasion depth of <1 mm was 17.1% (7/41), 1-<3 mm was 19.0% (16/84), and 3-5 mm was 3/10, with no significant difference among three groups (χ(2)=0.870, P=0.647). Logistic regression analysis showed positive cone margin (OR=5.069, P=0.014) and age (OR=1.080, P=0.024) were the independent risk factors of residual lesions after LEEP conization. CONCLUSIONS: CDB alone is not adequate for the diagnosis of MCC. For young patients who desire to preserve fertility with a negative cone margin, close follow-up is acceptable. Cone margin status and age are two independent risk factors for residual lesions after LEEP.
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Cuello del Útero/patología , Colposcopía/métodos , Electrocirugia/métodos , Displasia del Cuello del Útero/patología , Displasia del Cuello del Útero/cirugía , Neoplasias del Cuello Uterino/patología , Neoplasias del Cuello Uterino/cirugía , Adulto , Anciano , Conización , Femenino , Estudios de Seguimiento , Humanos , Histerectomía , Persona de Mediana Edad , Cuello , Valor Predictivo de las Pruebas , Embarazo , Estudios Retrospectivos , Factores de Riesgo , Sensibilidad y EspecificidadRESUMEN
Smoking among Malaysian adolescents remains a public health concern despite concerted efforts in tobacco control. The aims of this study were to examine the prevalence and determinants of current-smoking status in young adolescents. This cross sectional study used the first round of the Malaysian Health and Adolescents Research Team's prospective cohort study. It was conducted in three States of the Central and Northern regions of Peninsular Malaysia between March and May 2012. The study used the multistage stratified sampling design. A total of 1,342 adolescents of both sexes, aged 12-13 years, were sampled from randomly selected urban and rural national schools. Information on current smoking status and associated factors were collected by a self-administered, pre-tested, validated, structured questionnaire. Seven percent of the samples were current-smokers; the majority (62%) of them started smoking at the age of 11 years or below. The prevalence of current smoking was significantly higher in males (odds ratio [OR] = 2.37; 95% CI: 1.46, 3.84), those who were influenced by smoker friends (OR = 8.35; 95% CI: 4.90, 14.25), who were unaware of the health risks of smoking (OR =1.85; 95% CI: 1.02, 3.36) and who reported a lack of satisfaction about their overall life (OR =3.26; 95% CI: 1.73, 6.12). The study findings provide valuable information to strengthen the existing school-based smoking prevention program through integration of social competence and social influence curricula. The program should empower the young adolescents to refuse tobacco offers, to overcome social influences and to resist peer pressure to avoid starting smoking. Particular focuses to include mental health service to prevent both emotional and behavioural problems are needed.
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Instituciones Académicas , Prevención del Hábito de Fumar , Fumar/epidemiología , Adolescente , Niño , Estudios de Cohortes , Estudios Transversales , Femenino , Humanos , Malasia/epidemiología , Masculino , Grupo Paritario , Estudios Prospectivos , Factores de Riesgo , Población Rural , Servicios de Salud Escolar , Instituciones Académicas/estadística & datos numéricos , Fumar/psicología , Población UrbanaRESUMEN
OBJECTIVE: The objective of the study is to assess the socioeconomic status of the households affected by the tsunami of 2004 & to determine the factors associated with the recovery of household economic status. METHODS: The study was conducted in tsunami-affected areas in Malaysia in 2010-2011. A total of 193 households were included in the survey. Multivariate logistic regression was performed to determine the factors related to the recovery of households' economic status. FINDINGS: Among 193 households, 37% were in a better condition, 40% were unchanged and 22% had not recovered. It took 2.2 years to get back to pre-disaster economic status. Factors leading to successful household economic recovery were "household resided in Sungai Petani", "belong to highest income quartile" and "age of household head". In contrast, "extended family type" and "unemployed household head" reduced the odds of recovery. Households which lost their fishing boats during the tsunami had less chance to recover their previous status. CONCLUSION: The findings of our study would be useful for policy consideration and planning of post disaster management in order to enhance the recovery of household economic status in the short period.
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Desastres/economía , Tsunamis/economía , Adulto , Factores de Edad , Anciano , Planificación en Desastres/economía , Composición Familiar , Femenino , Humanos , Renta/estadística & datos numéricos , Malasia , Masculino , Persona de Mediana Edad , Política Pública , Factores Sexuales , Factores Socioeconómicos , Encuestas y CuestionariosRESUMEN
When students answer an in-class conceptual question individually using clickers, discuss it with their neighbors, and then revote on the same question, the percentage of correct answers typically increases. This outcome could result from gains in understanding during discussion, or simply from peer influence of knowledgeable students on their neighbors. To distinguish between these alternatives in an undergraduate genetics course, we followed the above exercise with a second, similar (isomorphic) question on the same concept that students answered individually. Our results indicate that peer discussion enhances understanding, even when none of the students in a discussion group originally knows the correct answer.
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Genética/educación , Aprendizaje , Grupo Paritario , Enseñanza/métodos , Comprensión , Evaluación Educacional , HumanosRESUMEN
Drosophila double park encodes a homolog of Cdt1 that functions in initiation of DNA replication in fission yeast and Xenopus. dup mutants complete the first 15 embryonic cell cycles, presumably via maternal dup products, and show defects in the 16(th) S phase (S16). Cells carrying dup(a1) allele forgo S16 altogether but enter mitosis 16 (M16). We find that the timing of entry into M16 is similar in dup(a1) and heterozygous or wild-type (wt) controls. In contrast, we find that mutant cells carrying another allele, dup(a3), undergo a partial S16 and delay the entry into M16. Thus, initiation of S16 appears necessary for delaying M16. This delay is absent in double mutants of dup(a3) and mei-41 (Drosophila ATR), indicating that a mei-41-dependent checkpoint acts to delay the entry into mitosis in response to incomplete DNA replication. dup(a3) and dup(a1) mutant cells that enter M16 become arrested in M16. We find that mitotic cyclins are stabilized and that a spindle checkpoint protein, Bub1, localizes onto chromosomes during mitotic arrest in dup mutants. These features suggest an arrest prior to metaphase-anaphase transition. dup(a3) bub1 double mutant cells exit M16, indicating that a bub1-mediated checkpoint acts to block mitotic exit in dup mutants. To our knowledge, this is the first report of (1) incomplete DNA replication affecting both the entry into and the exit from mitosis in a single cell cycle via different mechanisms and (2) the role of bub1 in regulating mitotic exit in response to incomplete DNA replication.
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Proteínas de Ciclo Celular/metabolismo , Replicación del ADN/fisiología , Proteínas de Drosophila/metabolismo , Drosophila/embriología , Mitosis/fisiología , Proteínas Quinasas/metabolismo , Alelos , Anafase/fisiología , Animales , Cromosomas/genética , Ciclinas/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Drosophila/metabolismo , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Metafase/fisiología , Mutación/genética , Proteínas Serina-Treonina Quinasas , Huso Acromático/metabolismoRESUMEN
Drosophila 14-3-3 epsilon and 14-3-3 zeta proteins have been shown to function in RAS/MAP kinase pathways that influence the differentiation of the adult eye and the embryo. Because 14-3-3 proteins have a conserved involvement in cell cycle checkpoints in other systems, we asked (1) whether Drosophila 14-3-3 proteins also function in cell cycle regulation, and (2) whether cell proliferation during Drosophila development has different requirements for the two 14-3-3 proteins. We find that antibody staining for 14-3-3 family members is cytoplasmic in interphase and perichromosomal in mitosis. Using mutants of cyclins, Cdk1 and Cdc25(string) to manipulate Cdk1 activity, we found that the localization of 14-3-3 proteins is coupled to Cdk1 activity and cell cycle stage. Relocalization of 14-3-3 proteins with cell cycle progression suggested cell-cycle-specific roles. This notion is confirmed by the phenotypes of 14-3-3 epsilon and 14-3-3 zeta mutants: 14-3-3 epsilon is required to time mitosis in undisturbed post-blastoderm cell cycles and to delay mitosis following irradiation; 14-3-3 zeta is required for normal chromosome separation during syncytial mitoses. We suggest a model in which 14-3-3 proteins act in the undisturbed cell cycle to set a threshold for entry into mitosis by suppressing Cdk1 activity, to block mitosis following radiation damage and to facilitate proper exit from mitosis.
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Drosophila/citología , Mitosis/fisiología , Tirosina 3-Monooxigenasa/genética , Tirosina 3-Monooxigenasa/metabolismo , Proteínas 14-3-3 , Animales , Proteína Quinasa CDC2/metabolismo , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Drosophila/crecimiento & desarrollo , Embrión no Mamífero/metabolismo , Femenino , Regulación del Desarrollo de la Expresión Génica , Sistema de Señalización de MAP Quinasas/fisiología , MasculinoRESUMEN
BACKGROUND: In response to DNA damage, fission yeast, mammalian cells, and cells of the Drosophila gastrula inhibit Cdk1 to delay the entry into mitosis. In contrast, budding yeast delays metaphase-anaphase transition by stabilization of an anaphase inhibitor, Pds1p. A variation of the second response is seen in Drosophila cleavage embryos; when nuclei enter mitosis with damaged DNA, centrosomes lose gamma-tubulin, spindles lose astral microtubules, chromosomes fail to reach a metaphase configuration, and interphase resumes without an intervening anaphase. The resulting polyploid nuclei are eliminated. RESULTS: The cells of the Drosophila gastrula can also delay metaphase-anaphase transition in response to DNA damage. This delay accompanies the stabilization of Cyclin A, a known inhibitor of sister chromosome separation in Drosophila. Unlike in cleavage embryos, gamma-tubulin remains at the spindle poles, and anaphase always occurs after the delay. Cyclin A mutants fail to delay metaphase-anaphase transition after irradiation and show an increased frequency of chromosome breakage in the subsequent anaphase. CONCLUSIONS: DNA damage delays metaphase-anaphase transition in Drosophila by stabilizing Cyclin A. This delay may normally serve to preserve chromosomal integrity during segregation. To our knowledge this is the first report of a metazoan metaphase-anaphase transition being delayed in response to DNA damage. Though mitotic progression is modulated in response to DNA damage in both cleaving and gastruating embryos of Drosophila, different mechanisms operate. These differences are discussed in the context of differential cell cycle regulation in cleavage and gastrula stages.
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Anafase/fisiología , Ciclina A/fisiología , Daño del ADN , Drosophila/embriología , Gástrula/citología , Metafase/fisiología , Animales , Ciclina A/genética , Drosophila/genética , Metilmetanosulfonato/farmacología , Mutación , Rayos XRESUMEN
The cell-division cycle is an orchestrated sequence of events that results in the duplication of a cell. In metazoa, cell proliferation is regulated in response to differentiation signals and body-size parameters, which either induce cell duplication or arrest the cell cycle, to ensure that organs develop to the correct size. In addition, the cell cycle may be altered to meet specialized requirements. This can be seen in the rapid cleavage cycles of vertebrates and insects that lack gap phases, in the nested S phases of Drosophila, and in the endocycles of nematodes, insects, plants and mammals that lack mitosis. Here we present the various modes of cell-cycle regulation in metazoa and discuss their possible generation by a combination of universally conserved molecules and new regulatory circuits.
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División Celular/fisiología , Drosophila/embriología , Regulación del Desarrollo de la Expresión Génica/fisiología , Vertebrados/embriología , Animales , Drosophila/citología , Drosophila/genética , Genes cdc/fisiología , Humanos , Transducción de Señal/genética , Vertebrados/anatomía & histología , Vertebrados/genética , Levaduras/citología , Levaduras/genética , Levaduras/crecimiento & desarrolloRESUMEN
Both growth (increase in mass) and proliferation (increase in cell number) contribute to the formation of multicellular organisms. We would like to understand the mechanisms that normally regulate growth and proliferation because breakdown of these mechanisms may be the basis for uncontrolled growth and proliferation that are associated with cancerous transformation and tumor progression. We review here classical and recent literature from diverse experimental systems that pertains to the regulation of mass and cell number.
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División Celular , Embrión de Mamíferos/fisiología , Desarrollo Embrionario , Animales , Apoptosis , Recuento de Células , Tamaño de la Célula , Drosophila melanogaster/embriología , Embrión de Mamíferos/citología , Embrión no Mamífero/citología , Matriz Extracelular/fisiología , HumanosRESUMEN
When cells enter mitosis with DNA that is unfit to be segregated, the consequences appear to be loss of centrosome function, abnormal spindles and a failure to segregate chromosomes. These defects may result from the workings of a surveillance mechanism that acts to cull irreparable nuclei.
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Centrosoma/fisiología , Daño del ADN , Mitosis/fisiología , Animales , Drosophila/fisiología , Modelos GenéticosRESUMEN
BACKGROUND: Studies in unicellular systems have established that DNA damage by irradiation invokes a checkpoint that acts to stall cell division. During metazoan development, the modulation of cell division by checkpoints must occur in the context of gastrulation, differential gene expression and changes in cell cycle regulation. To understand the effects of checkpoint activation in a developmental context, we examined the effect of X-rays on post-blastoderm embryos of Drosophila melanogaster. RESULTS: In Drosophila, DNA damage was previously found to delay anaphase chromosome separation during cleavage cycles that lack a G2 phase. In post-blastoderm cycles that included a G2 phase, we found that irradiation delayed the entry into mitosis. Gastrulation and the developmental program of string (Cdc25) gene expression, which normally regulates the timing of mitosis, occurred normally after irradiation. The radiation-induced delay of mitosis accompanied the exclusion of mitotic cyclins from the nucleus. Furthermore, a mutant form of the mitotic kinase Cdk1 that cannot be inhibited by phosphorylation drove a mitotic cyclin into the nucleus and overcame the delay of mitosis induced by irradiation. CONCLUSIONS: Developmental changes in the cell cycle, for example, the introduction of a G2 phase, dictate the response to checkpoint activation, for example, delaying mitosis instead of or in addition to delaying anaphase. This unprecedented finding suggests that different mechanisms are used at different points during metazoan development to stall cell division in response to checkpoint activation. The delay of mitosis in post-blastoderm embryos is due primarily to inhibitory phosphorylation of Cdk1, whereas nuclear exclusion of a cyclin-Cdk1 complex might play a secondary role. Delaying cell division has little effect on gastrulation and developmentally regulated string gene expression, supporting the view that development generally dictates cell proliferation and not vice versa.
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Daño del ADN , Proteínas de Drosophila , Embrión no Mamífero/efectos de la radiación , Genes cdc , Mitosis/efectos de la radiación , Proteínas Tirosina Fosfatasas , Animales , Blastodermo/fisiología , Ciclo Celular/efectos de la radiación , Proteínas de Ciclo Celular , Ciclinas/genética , Ciclinas/metabolismo , Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Drosophila melanogaster/efectos de la radiación , Embrión no Mamífero/citología , Regulación del Desarrollo de la Expresión Génica , Respuesta al Choque Térmico , Fosfoproteínas Fosfatasas/genética , Fosfoproteínas Fosfatasas/metabolismo , Coloración y EtiquetadoRESUMEN
The Drosophila grapes (grp) gene, which encodes a homolog of the Schizosaccharomyces pombe Chk1 kinase, provides a cell-cycle checkpoint that delays mitosis in response to inhibition of DNA replication [1]. Grp is also required in the undisturbed early embryonic cycles: in its absence, mitotic abnormalities appear in cycle 12 and chromosomes fail to fully separate in subsequent cycles [2] [3]. In other systems, Chk1 kinase phosphorylates and suppresses the activity of Cdc25 phosphatase: the resulting failure to remove inhibitory phosphate from cyclin-dependent kinase 1 (Cdk1) prevents entry into mitosis [4] [5]. Because in Drosophila embryos Cdk1 lacks inhibitory phosphate during cycles 11-13 [6], it is not clear that known actions of Grp/Chk1 suffice in these cycles. We found that the loss of grp compromised cyclin A proteolysis and delayed mitotic disjunction of sister chromosomes. These defects occurred before previously reported grp phenotypes. We conclude that Grp activates cyclin A degradation, and functions to time the disjunction of chromosomes in the early embryo. As cyclin A destruction is required for sister chromosome separation [7], a failure in Grp-promoted cyclin destruction can also explain the mitotic phenotype. The mitotic failure described previously for cycle 12 grp embryos might be a more severe form of the phenotypes that we describe in earlier embryos and we suggest that the underlying defect is reduced degradation of cyclin A.
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Ciclina A/metabolismo , Drosophila/crecimiento & desarrollo , Drosophila/genética , Proteínas Quinasas/fisiología , Anafase/genética , Animales , Western Blotting , Ciclo Celular/efectos de los fármacos , Ciclo Celular/genética , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1) , Cicloheximida/farmacología , ADN/análisis , Drosophila/citología , Drosophila/enzimología , Proteínas de Drosophila , Microscopía Fluorescente , Proteínas Quinasas/genética , Inhibidores de la Síntesis de la Proteína/farmacología , Proteínas de Schizosaccharomyces pombeRESUMEN
Division subdivides mass without increasing it. So one should not expect that an increase in cell division would make an organism bigger. Both classic and recent experiments confirm this simple rationale: altering proliferation produces normally sized body structures with either especially small or exceptionally large cells.
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Proteínas Portadoras , División Celular , Proteínas de Unión al ADN , Proteínas de Drosophila , Crecimiento/fisiología , Transactivadores , Animales , Proteína Quinasa CDC2/fisiología , Proteínas de Ciclo Celular/fisiología , Tamaño de la Célula , Drosophila melanogaster/citología , Drosophila melanogaster/embriología , Drosophila melanogaster/crecimiento & desarrollo , Factores de Transcripción E2F , Embrión no Mamífero , Proteínas de Insectos/fisiología , Fosfoproteínas Fosfatasas/fisiología , Pupa , Proteína 1 de Unión a Retinoblastoma , Factores de Transcripción/deficiencia , Factores de Transcripción/fisiología , Alas de Animales/citología , Alas de Animales/embriología , Alas de Animales/crecimiento & desarrollo , Fosfatasas cdc25RESUMEN
The germ cells of metazoans follow a program of proliferation that is distinct from proliferation programs of somatic cells. Despite their developmental importance, the cell proliferation program in the metazoan primordial germ cells is not well characterized and the regulatory controls are not understood. In Drosophila melanogaster, germ cell precursors (called pole cells) proliferate early in embryogenesis and then enter a prolonged quiescence. We found that polar nuclear divisions are asynchronous and lag behind somatic nuclear divisions during syncytial cycles 9 and 10. Thus, the polar division program deviates from the somatic division program when pole nuclei and somatic nuclei still share a common cytoplasm, earlier than previously thought. The lag in polar nuclear divisions is independent of grapes, which is required for lengthening somatic cell cycles 10-13. Mapping of the last S phase in pole cells and measurement of their DNA content indicate that pole cells become quiescent in G2 phase of the cell cycle. We were able to drive quiescent pole cells into mitosis by induction of either an activator of Cdc2 (Cdc25string phosphatase) or a mutant form of Cdc2 that cannot be inhibited by phosphorylation. In contrast, induction of wild-type Cdc2 with a mitotic cyclin did not induce mitosis in pole cells. We propose that inhibition of Cdc2 by phosphorylation contributes to G2 arrest in pole cells during embryogenesis. Furthermore, pole cells enter G1 following induced mitoses, indicating that entry into both mitosis and S phase is blocked in quiescent pole cells. These studies represent the first molecular characterization of proliferation in embryonic germ cells of Drosophila.
Asunto(s)
Proteína Quinasa CDC2/fisiología , Ciclo Celular/fisiología , Drosophila melanogaster/embriología , Células Germinativas/citología , Animales , Proteínas de Ciclo Celular/metabolismo , Ciclina A/análisis , Ciclina A/farmacología , Replicación del ADN , Drosophila melanogaster/citología , Embrión no Mamífero/química , Activación Enzimática , Fase G2/fisiología , Histonas/análisis , Mitosis , Fosfoproteínas Fosfatasas/metabolismo , Fosforilación , Fosfatasas cdc25RESUMEN
The cyclin proteolysis that accompanies the exit from mitosis in diverse systems appears to be essential for restoration of interphase. The early syncytial divisions of Drosophila embryos, however, occur without detectable oscillations in the total cyclin level or Cdk1 activity. Nonetheless, we found that injection of an established inhibitor of cyclin proteolysis, a cyclin B amino-terminal peptide, prevents exit from mitosis in syncytial embryos. Similarly, injection of a version of Drosophila cyclin B that is refractory to proteolysis results in mitotic arrest. We infer that proteolysis of cyclins is required for exit from syncytial mitoses. This inference can be reconciled with the failure to observe oscillations in total cyclin levels if only a small pool of cyclins is destroyed in each cycle. We find that antibody detection of histone H3 phosphorylation (PH3) acts as a reporter for Cdk1 activity. A gradient of PH3 along anaphase chromosomes suggests local Cdk1 inactivation near the spindle poles in syncytial embryos. This pattern of Cdk1 inactivation would be consistent with local cyclin destruction at centrosomes or kinetochores. The local loss of PH3 during anaphase is specific to the syncytial divisions and is not observed after cellularization. We suggest that exit from mitosis in syncytial cycles is modified to allow nuclear autonomy within a common cytoplasm.
Asunto(s)
Ciclinas/metabolismo , Drosophila melanogaster/citología , Histonas/metabolismo , Proteínas de Insectos/metabolismo , Mitosis/fisiología , Procesamiento Proteico-Postraduccional , Animales , Proteína Quinasa CDC2/genética , Proteína Quinasa CDC2/fisiología , Núcleo Celular/ultraestructura , Citoplasma/ultraestructura , Drosophila melanogaster/embriología , Embrión no Mamífero/citología , Regulación del Desarrollo de la Expresión Génica , Células Gigantes/citología , Proteínas HSP70 de Choque Térmico/genética , Fosforilación , Regiones Promotoras Genéticas , Proteínas Recombinantes de Fusión/metabolismo , TemperaturaRESUMEN
Minichromosome maintenance (MCM) proteins are essential eukaryotic DNA replication factors. The binding of MCMs to chromatin oscillates in conjunction with progress through the mitotic cell cycle. This oscillation is thought to play an important role in coupling DNA replication to mitosis and limiting chromosome duplication to once per cell cycle. The coupling of DNA replication to mitosis is absent in Drosophila endoreplication cycles (endocycles), during which discrete rounds of chromosome duplication occur without intervening mitoses. We examined the behavior of MCM proteins in endoreplicating larval salivary glands, to determine whether oscillation of MCM-chromosome localization occurs in conjunction with passage through an endocycle S phase. We found that MCMs in polytene nuclei exist in two states: associated with or dissociated from chromosomes. We demonstrate that cyclin E can drive chromosome association of DmMCM2 and that DNA synthesis erases this association. We conclude that mitosis is not required for oscillations in chromosome binding of MCMs and propose that cycles of MCM-chromosome association normally occur in endocycles. These results are discussed in a model in which the cycle of MCM-chromosome associations is uncoupled from mitosis because of the distinctive program of cyclin expression in endocycles.