RESUMEN
BACKGROUND AND OBJECTIVES: A decade ago, the Association of Family Medicine Residency Directors developed the Residency Performance Index (RPI) as a novel dashboard of metrics to support residency programs' quality improvement efforts. Although the RPI has since been discontinued, we sought to identify lessons learned from an analysis of 6 years of data collected while the RPI was in use to inform future quality and accreditation efforts implemented at the national level. METHODS: The RPI collected data from 2012-2017 for nearly 250 distinct family medicine residency programs, identifying strengths and areas for improvement. Eighty-two programs provided data for 3 or more years of measures allowing analysis of improvement trends. RESULTS: For participating programs, aggregate data over 6 years indicated the majority had stable leadership and accreditation. Total family medicine center (FMC) visits by graduates and resident visit demographics were robust. Graduate scope of practice was consistent with nationally publicized trends. Programs hit most aspirational targets more than 40% of the time. However, analysis for those programs with 3 or more years of data revealed that the tool did not result in significant changes for most metrics. Linear regression analysis showed improvements in total patient visits, visits under 10 years of age, and certain procedural competencies for those programs with 3 or more years of data. CONCLUSIONS: The RPI was the first and only nationally utilized family medicine graduate medical education quality improvement tool. Individual programs did not show substantial change in quantifiable metrics over time despite limited evidence of select programmatic improvements. Nationally, aggregated data provided insight into scope of practice and other areas of interest in residency training. Further efforts in provision of residency improvement tools are important to support programs given the increasing complexity and high stakes of family medicine residency education.
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Internado y Residencia , Acreditación , Educación de Postgrado en Medicina , Medicina Familiar y Comunitaria/educación , Humanos , Encuestas y CuestionariosRESUMEN
RESEARCH QUESTION: Circulating soluble LH-HCG receptor (sLHCGR) is a first-trimester marker for screening pregnancy pathologies and predicts premature or multiple births before fertility treatment. Oestradiol per oocyte at ovulation induction predicts IVF treatment outcomes. We asked whether sLHCGR levels are stable during fertility treatment and whether, alone or with oestradiol, they could improve prediction of fertility treatment outcomes. DESIGN: Serum sLHCGR, anti-Müllerian hormone [AMH] and oestradiol were measured in patients undergoing IVF. Antral follicle count before ovarian stimulation and oocyte yield were used to establish sLHCGR- oocyte ratio (SOR), sLHCGR- antral follicle ratio (SAR), oestradiol at trigger per oocyte (oestradiol-oocyte ratio [EOR]) and oestradiol at trigger per antral follicle (oestradiol-antral follicle ratio [EAR]). RESULTS: The relatively stable sLHCGR was negatively related to AMH when oocyte yield was high. The sLHCGR levels were proportional (râ¯=â¯0.49) to oestradiol at early cycle (day-3). Pregnancy and live birth were highest at low sLHCGR (≤1.0 pmol/ml) and SOR (≤ 0.1 pmol/ml/oocyte). A total of 86-89% of live births in IVF treatment were within the cut-off parameters of SAR and SOR (0.5 pmol/ml) and EAR and EOR (380 pg/ml). For failed pregnancy, age, SOR and EOR together had positive and negative predictive values of 0.841 and 0.703, respectively. CONCLUSIONS: sLHCGR levels are negatively related to AMH when oocyte yield is high. High early cycle sLHCGR is associated with elevated day-3 oestradiol. Low sLHCGR and SOR are indicators of increased clinical pregnancy and live birth rates. Patient age and SOR, combined with EOR, might improve prediction of IVF treatment outcomes.
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Estradiol/sangre , Fertilización In Vitro , Nacimiento Vivo , Índice de Embarazo , Receptores de HL/sangre , Adulto , Hormona Antimülleriana/sangre , Femenino , Humanos , Folículo Ovárico , Inducción de la Ovulación , Embarazo , Resultado del EmbarazoRESUMEN
In addition to its roles in transcription and replication, topoisomerase 2 (topo 2) is crucial in shaping mitotic chromosomes and in ensuring the orderly separation of sister chromatids. As well as its recruitment throughout the length of the mitotic chromosome, topo 2 accumulates at the primary constriction. Here, following cohesin release, the enzymatic activity of topo 2 acts to remove residual sister catenations. Intriguingly, topo 2 does not bind and cleave all sites in the genome equally; one preferred site of cleavage is within the core centromere. Discrete topo 2-centromeric cleavage sites have been identified in α-satellite DNA arrays of active human centromeres and in the centromere regions of some protozoans. In this study, we show that topo 2 cleavage sites are also a feature of the centromere in Schizosaccharomyces pombe, the metazoan Drosophila melanogaster and in another vertebrate species, Gallus gallus (chicken). In vertebrates, we show that this site-specific cleavage is diminished by depletion of CENP-I, an essential constitutive centromere protein. The presence, within the core centromere of a wide range of eukaryotes, of precise sites hypersensitive to topo 2 cleavage suggests that these mark a fundamental and conserved aspect of this functional domain, such as a non-canonical secondary structure.
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Centrómero/genética , ADN-Topoisomerasas de Tipo II/metabolismo , Animales , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Centrómero/metabolismo , Proteína A Centromérica/metabolismo , Pollos , Proteínas Cromosómicas no Histona/metabolismo , ADN Satélite/genética , Drosophila melanogaster , Humanos , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , CohesinasRESUMEN
The luteinizing hormone (LH) and pregnancy hormone, human chorionic gonadotrophin (hCG), share a common receptor: LH/hCG-R or LHCGR. In this prospective study involving 290 patients undergoing in vitro fertilization (IVF) and embryo transfer, we have examined whether pretreatment circulating LHCGR (sLHCGR) influences the course of pregnancy and perinatal outcome after embryo transfer. The blood samples were collected before the fertility treatment began and sLHCGR concentrations were measured using an enzyme-linked immunosorbent assay (ELISA) test. We demonstrate that extreme pretreatment sLHCGR concentrations (low & high) were linked to abnormal birth weights for singleton births, while very low concentrations of sLHCGR were associated with premature delivery (≤34 weeks) of singletons and multiple births following transfer of ≥2 embryos.
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Progenie de Nacimiento Múltiple , Resultado del Embarazo , Nacimiento Prematuro/sangre , Receptores de HL/sangre , Transferencia de Embrión , Femenino , Fertilización In Vitro , Humanos , Recién Nacido , Embarazo , Embarazo Múltiple , Estudios ProspectivosRESUMEN
BACKGROUND: In 2013, the World Organisation of Family Doctors published training standards for post-graduate medical education (GME) in Family Medicine/General Practice (FP/GP). GME quality has not been well-defined, other than meeting accreditation standards. In 2009, the Association of Family Medicine Residency Directors (AFMRD) developed a tool that would aid in raising the quality of family medicine residency training in the USA. OBJECTIVE: We describe the development of this quality improvement tool, which we called the residency performance index (RPI), and its first three years of use by US family medicine residency (FMR) programmes. The RPI uses metrics specific to family medicine training in the USA to help programmes identify strengths and areas for improvement in their educational activities. Our review of three years of experience with the RPI revealed difficulties with collecting data, and lack of information on graduates' scope of practice. It also showed the potential usefulness of the tool as a programme improvement mechanism. CONCLUSIONS: The RPI is a nationwide, standardised, programme quality improvement tool for family medicine residency programmes in the USA, which was successfully launched as part of AFMRD's strategic plan. Although some initial challenges need to be addressed, it has the promise to aid family medicine residencies in their internal improvement efforts. This model could be adapted in other post-graduate training settings in FM/GP around the world.
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Educación de Postgrado en Medicina/normas , Medicina Familiar y Comunitaria/educación , Médicos Generales/educación , Internado y Residencia/normas , Mejoramiento de la Calidad , Educación de Postgrado en Medicina/organización & administración , Medicina Familiar y Comunitaria/normas , Médicos Generales/normas , Humanos , Internado y Residencia/organización & administración , Estados UnidosRESUMEN
Sprouty proteins are regulators of cell growth and branching morphogenesis. Unlike mouse Spry3, which is X-linked, human SPRY3 maps to the pseudoautosomal region 2; however, the human Y-linked allele is not expressed due to epigenetic silencing by an unknown mechanism. SPRY3 maps adjacent to X-linked Trimethyllysine hydroxylase epsilon (TMLHE), recently identified as an autism susceptibility gene. We report that Spry3 is highly expressed in central and peripheral nervous system ganglion cells in mouse and human, including cerebellar Purkinje cells and retinal ganglion cells. Transient over-expression or knockdown of Spry3 in cultured mouse superior cervical ganglion cells inhibits and promotes, respectively, neurite growth and branching. A 0.7 kb gene fragment spanning the human SPRY3 transcriptional start site recapitulates the endogenous Spry3-expression pattern in LacZ reporter mice. In the human and mouse the SPRY3 promoter contains an AG-rich repeat and we found co-expression, and promoter binding and/or regulation of SPRY3 expression by transcription factors MAZ, EGR1, ZNF263 and PAX6. We identified eight alleles of the human SPRY3 promoter repeat in Caucasians, and similar allele frequencies in autism families. We characterized multiple SPRY3 transcripts originating at two CpG islands in the X-linked F8A3-TMLHE region, suggesting X chromosome regulation of SPRY3. These findings provide an explanation for differential regulation of X and Y-linked SPRY3 alleles. In addition, the presence of a SPRY3 transcript exon in a previously described X chromosome deletion associated with autism, and the cerebellar interlobular variation in Spry3 expression coincident with the reported pattern of Purkinje cell loss in autism, suggest SPRY3 as a candidate susceptibility locus for autism.
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Trastorno Autístico/genética , Cromosomas Humanos X , Predisposición Genética a la Enfermedad , Péptidos y Proteínas de Señalización Intracelular/genética , Regiones Promotoras Genéticas , Receptor PAR-2/genética , Alelos , Animales , Composición de Base , Secuencia de Bases , Línea Celular , Cerebelo/metabolismo , Islas de CpG , Metilación de ADN , Modelos Animales de Enfermedad , Exones , Ganglios/metabolismo , Expresión Génica , Regulación de la Expresión Génica , Genes Ligados a X , Sitios Genéticos , Humanos , Ratones , Ratones Transgénicos , Datos de Secuencia Molecular , Neuritas/metabolismo , Polimorfismo Genético , Alineación de Secuencia , Factores de Transcripción/metabolismo , Transcripción GenéticaRESUMEN
OBJECTIVE: To explore the value of circulating luteinizing human chorionic gonadotropin receptor (LHCGR) forms for the prediction of preeclampsia (PE) in the first trimester of pregnancy. METHODS: Case-control study, based on a cohort of 5,759 pregnancies, including 20 early PE, 20 late PE, and 300 controls. We recorded/measured maternal characteristics, mean arterial pressure (MAP), uterine artery (UtA) Doppler, placental growth factor (PlGF), soluble Fms-like tyrosine kinase-1 (sFtl-1), and LHCGR forms (hCG-LHCGR and soluble LHCGR), and their independent predictive values were analyzed by logistic regression. RESULTS: For early PE, the model included black ethnicity, chronic hypertension, previous PE, MAP, UtA Doppler, PlGF, sFlt-1, and LHCGR forms, achieving detection rates (DR) of 83% at 10% of false-positive rates (FPR) [AUC: 0.961 (95% CI: 0.921-1)]. For late PE, the model included body mass index, previous PE, UtA Doppler, PlGF, sFlt-1, and LHCGR forms, with DR of 75% at 10% of FPR [AUC: 0.923 (95% CI: 0.871-0.976)]. In both early and late PE, LHCGR forms improved DR by 6-15%. CONCLUSIONS: LHCGR forms improved the prediction for early and late PE. These results should be confirmed in larger prospective studies.
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Preeclampsia/sangre , Preeclampsia/diagnóstico por imagen , Primer Trimestre del Embarazo/sangre , Receptores de HL/sangre , Adulto , Biomarcadores/sangre , Estudios de Casos y Controles , Estudios de Cohortes , Femenino , Humanos , Valor Predictivo de las Pruebas , Embarazo , Estudios Prospectivos , UltrasonografíaRESUMEN
BACKGROUND: Previous studies showed that soluble LHCGR/hCG-sLHCGR concentrations in serum or plasma combined with PAPP-A and free ßhCG significantly increased the sensitivity of Down's syndrome screen at early pregnancy without altering the false positive rate. The goal of the present study was to further examine the role of sLHCGR forms as combinatorial markers and to investigate whether sLHCGR could serve as an independent biomarker for Down's syndrome in first trimester pregnancy screens. METHODS: The PAPP-A, free ßhCG, and hCG-sLHCGR concentrations together with nuchal translucency (NT) were measured in 40 Down's and 300 control pregnancies. The sLHCGR concentration was analysed in 40 Down's and 206 control pregnancies. RESULTS: The hCG-LHCGR in combination with PAPP-A and free ßhCG increased the detection rate (DR) by 35% without altering the false positive rate (FPR). The sLHCGR: hCG-sLHCGR ratio alone detected 80% of Down's pregnancies in first trimester screening, with a false positive rate of 0.5%. CONCLUSIONS: While measurement of sLHCGR forms in combination with PAPP-A and free ßhCG significantly increases the detection rate of Down's syndrome at first trimester, the ratio of sLHCGR: hCG-sLHCGR acts as an independent marker with a detection rate that is significantly higher than the existing biochemical markers individually for prenatal first trimester screening of Down's syndrome.
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Gonadotropina Coriónica Humana de Subunidad beta/sangre , Síndrome de Down/diagnóstico , Diagnóstico Prenatal/métodos , Receptores de HL/sangre , Área Bajo la Curva , Biomarcadores/sangre , Estudios de Casos y Controles , Reacciones Falso Positivas , Femenino , Humanos , Medida de Translucencia Nucal , Valor Predictivo de las Pruebas , Embarazo , Primer Trimestre del Embarazo/sangre , Proteína Plasmática A Asociada al Embarazo/metabolismo , Curva ROC , Estudios RetrospectivosRESUMEN
BACKGROUND: Residency programs are increasingly being asked to defend their quality, and that of the residents they produce. Yet "residency quality" is a construct that has not been well defined, with no accepted standards other than meeting accreditation standards. In 2009, the Association of Family Medicine Residency Directors developed a strategic plan that included the goal of raising the quality of family medicine training. OBJECTIVE: We describe the development of this quality improvement tool, which we called the residency performance index (RPI), and its first year of use by family medicine residency programs. We describe the use of the tool as a "dashboard" to facilitate program self-improvement. INTERVENTION: Using program metrics specific to family medicine training, and benchmark criteria for these metrics, the RPI was launched in 2012 to help programs identify strengths and areas for improvement in their educational activities and resident clinical experiences that could be tracked and reviewed as part of the annual program evaluation. RESULTS: Approximately 100 program directors began using the tool and 70 finished the process, and were provided aggregate data. Initial review of this experience revealed difficulties with collecting data, and lack of information on graduates' scope of practice. It also showed the potential usefulness of the tool as a program improvement mechanism. CONCLUSIONS: The RPI is a new quality improvement tool for family medicine residency programs. Although some initial challenges need to be addressed, it has the promise to aid family medicine residency in its internal improvement efforts.
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A central tenet of evolutionary explanations for ageing is that the strength of selection wanes with age. However, data on age-specific expression and benefits of sexually selected traits are lacking-particularly for traits subject to sexual conflict. We addressed this by using as a model the responses of Drosophila melanogaster females of different ages to receipt of sex peptide (SP), a seminal fluid protein transferred with sperm during mating. SP can mediate sexual conflict, benefitting males while causing fitness costs in females. Virgin and mated females of all ages showed significantly reduced receptivity in response to SP. However, only young virgin females also showed increased egg laying; hence, there was a narrow demographic window of maximal responses to SP. Males gained significant 'per mating' fitness benefits only when mating with young females. The pattern completely reversed in matings with older females, where SP transfer was costly. The overall benefits of SP transfer (hence opportunity for selection) therefore reversed with female age. The data reveal a new example of demographic variation in the strength of selection, with convergence and conflicts of interest between males and ageing females occurring over different facets of responses to a sexually antagonistic trait.
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Proteínas de Drosophila/fisiología , Drosophila melanogaster/fisiología , Preferencia en el Apareamiento Animal , Semen/química , Factores de Edad , Animales , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Eyaculación , Femenino , Fertilidad , Hormonas de Insectos , Masculino , ReproducciónRESUMEN
BACKGROUND: Soluble LH/hCG receptor (sLHCGR) released from placental explants and transfected cells can be detected in sera from pregnant women. To determine whether sLHCGR has diagnostic potential, quantitative ELISAs were developed and tested to examine the correlation between pregnancy outcome and levels of serum sLHCGR and hCG-sLHCGR complex. METHODS: Anti-LHCGR poly- and monoclonal antibodies recognizing defined LHCGR epitopes, commerical anti-hCGbeta antibody, together with recombinant LHCGR and yoked hCGbeta-LHCGR standard calibrators were used to develop two ELISAs. These assays were employed to quantify serum sLHCGR and hCG-sLHCGR at first trimester human pregnancy. RESULTS: Two ELISAs were developed and validated. Unlike any known biomarker, sLHCGR and hCG-sLHCGR are unique because Down's syndrome (DS), preeclampsia and preterm delivery are linked to both low (less than or equal to 5 pmol/mL), and high (equal to or greater than 170 pmol/mL) concentrations. At these cut-off values, serum hCG-sLHCGR together with PAPP-A detected additional DS pregnancies (21%) which were negative by free hCGbeta plus PAPP-A screening procedure. Therefore, sLHCGR/hCG-sLHCGR has an additive effect on the current primary biochemical screening of aneuploid pregnancies. More than 88% of pregnancies destined to end in fetal demise (stillbirth) exhibited very low serum hCG-sLHCGR(less than or equal to 5 pmol/mL) compared to controls (median 16.15 pmol/mL, n = 390). The frequency of high hCG-sLHCGR concentrations (equal to or greater than 170 pmol/mL) in pathological pregnancies was at least 3-6-fold higher than that of the control, suggesting possible modulation of the thyrotropic effect of hCG by sLHCGR. CONCLUSIONS: Serum sLHCGR/hCG-sLHCGR together with PAPP-A, have significant potential as first trimester screening markers for predicting pathological outcomes in pregnancy.
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Síndrome de Down/diagnóstico , Preeclampsia/diagnóstico , Primer Trimestre del Embarazo/sangre , Nacimiento Prematuro/diagnóstico , Receptores de HL/sangre , Adulto , Anticuerpos Monoclonales , Gonadotropina Coriónica Humana de Subunidad beta/sangre , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Enfermedades Fetales/diagnóstico , Humanos , Embarazo , Resultado del Embarazo , Proteína Plasmática A Asociada al Embarazo , Diagnóstico Prenatal/métodos , Estudios Prospectivos , Receptores de HL/inmunología , Reproducibilidad de los Resultados , Estudios Retrospectivos , Sensibilidad y Especificidad , MortinatoRESUMEN
BACKGROUND: Successful pregnancy via in vitro fertilization (IVF) depends on the recovery of an adequate number of healthy oocytes and on blastocyst implantation following uterine transfer. Two hormones, LH and hCG, utilize a common LH/hCG receptor (LHCGR), variations in which have profound implications in human reproduction. Soluble LHCGR (sLHCGR) is released from experimental cell lines and placental explants and it can be detected in the follicular fluid and serum. METHODS: To evaluate the impact of circulating soluble LHCGR (sLHCGR) in fertility treatment, we measured sLHCGR and LH-sLHCGR complex in serum from women seeking IVF using specifically developed quantitative enzyme-linked immunosorbent assays (ELISA). Following an IVF cycle of treatment, patients were grouped according to oocyte yield into low (lower than or equal to 7 oocytes), intermediate (8-14 oocytes) and high (greater than or equal to 15 oocytes) responders and pregnancy outcome noted. RESULTS: Pre-treatment sLHCGR identified many women at risk of ovarian hyperstimulation. Low levels of sLHCGR were associated with pregnancy in both high and low responders but sLHCGR did not significantly affect the treatment outcome of intermediate responders. Low responders who failed to become pregnant had high levels of circulating sLHCGR bound to LH (LH-sLHCGR). CONCLUSIONS: Pre-treatment measurement of sLHCGR could be used to tailor individual fertility treatment programs and improve outcomes by avoiding ovarian hyperstimulation and poor embryo implantation.
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Síndrome de Hiperestimulación Ovárica/sangre , Receptores de HL/sangre , Factores de Edad , Hormona Antimülleriana/sangre , Implantación del Embrión , Ensayo de Inmunoadsorción Enzimática , Femenino , Fertilización In Vitro , Humanos , Hormona Luteinizante/sangre , Inducción de la Ovulación , Embarazo , Resultado del Embarazo , Estudios Prospectivos , Factores de RiesgoRESUMEN
In our view, the conflict theory of imprinting explains the evolution of parental allele-specific gene expression patterns in the somatic tissues of mammals and angiosperms. Not surprisingly, given its importance in mammalian development and pathology, the evolution of imprinting continues to attract considerable interest from theoretical and experimental biologists. However, we contend that much of the ensuing debate is of poor quality. We discuss several problems with the manner in which workers in the field engage in this debate and we argue for a more formal approach to the discussion of theories of the evolution of imprinting.
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Evolución Biológica , Impresión Genómica/genética , Animales , HumanosRESUMEN
Topoisomerase II (topo II) is a major component of mitotic chromosomes, and its unique decatenating activity has been implicated in many aspects of chromosome dynamics, of which chromosome segregation is the most seriously affected by loss of topo II activity in living cells. There is considerable evidence that topo II plays a role at the centromere including: the centromere-specific accumulation of topo II protein; cytogenetic/molecular mapping of the catalytic activity of topo II to active centromeres; the influence of sumoylated topo II on sister centromere cohesion; and its involvement in the activation of a Mad2-dependent spindle checkpoint. By using a human cell line with a conditional-lethal mutation in the gene encoding DNA topoisomerase IIalpha, we find that depletion of topo IIalpha, while leading to a disorganised metaphase plate, does not have any overt effect on general assembly of kinetochores. Fluorescence in situ hybridisation suggested that centromeres segregate normally, most segregation errors being chromatin bridges involving longer chromosome arms. Strikingly, a linear human X centromere-based minichromosome also displayed a significantly increased rate of missegregation. This sensitivity to depletion of topo IIalpha might be linked to structural alterations within the centromere domain, as indicated by a significant shortening of the distance across metaphase sister centromeres and the abnormal persistence of PICH-coated connections between segregating chromatids.
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Anafase , ADN Helicasas/metabolismo , ADN-Topoisomerasas de Tipo II/deficiencia , Proteínas de Unión al ADN/deficiencia , Cinetocoros/metabolismo , Metafase , Antígenos de Neoplasias , Segregación Cromosómica , Cromosomas Humanos/metabolismo , Humanos , Isoenzimas/metabolismoRESUMEN
Chromosome engineering has allowed the generation of an extensive and well-defined series of linear human X centromere-based minichromosomes, which has been used to investigate the influence of size and structure on chromosome segregation in vertebrate cells. A clear relationship between overall chromosome size and mitotic stability was detected, with decreasing size associated with increasing loss rates. In chicken DT40, the lower size limit for prolonged mitotic stability is approximately 550 kb: at 450 kb, there was a dramatic increase in chromosome loss, while structures of approximately 200 kb could not be recovered. In human HT1080 cells, the size threshold for mitotic stability is approximately 1.6 Mb. Minichromosomes of 0.55-1.0 Mb can be recovered, but display high loss rates. However, all minichromosomes examined exhibited more segregation errors than normal chromosomes in HT1080 cells. This error rate increases with decreased size and correlates with reduced levels of CENP-A and Aurora B. In mouse LA-9 and Indian muntjac FM7 cells, the size requirements for mitotic stability are much greater. In mouse, a human 2.7-Mb minichromosome is rarely able to propagate a kinetochore and behaves acentrically. In Indian muntjac, CENP-C associates with the human minichromosome, but the mitotic apparatus appears unable to handle its segregation.
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Cromosomas , Vertebrados/genética , Animales , Secuencia de Bases , Southern Blotting , Centrómero , Pollos , Cromosomas Humanos X , Cartilla de ADN , ADN Recombinante , Electroforesis en Gel de Campo Pulsado , Humanos , Mitosis , Hibridación de Ácido NucleicoRESUMEN
Genomic imprinting causes parental origin-dependent differential expression of a small number of genes in mammalian and angiosperm plant embryos, resulting in non-Mendelian inheritance of phenotypic traits. The "conflict" theory of the evolution of imprinting proposes that reduced genetic relatedness of paternally, relative to maternally, derived alleles in offspring of polygamous females supports parental sex-specific selection at gene loci that influence maternal investment. While the theory's physiological predictions are well supported by observation, the requirement of polyandry in the evolution of imprinting from an ancestral Mendelian state has not been comprehensively analyzed. Here, we use diallelic models to examine the influence of various degrees of polyandry on the evolution of both Mendelian and imprinted autosomal gene loci that influence trade-offs between maternal fecundity and offspring viability. We show that, given a plausible assumption on the physiological relationship between maternal fecundity and offspring viability, low levels of polyandry are sufficient to reinforce exclusively the fixation of "greedy" paternally imprinted alleles that increase offspring viability at the expense of maternal fecundity and "thrifty" maternally imprinted alleles of opposite effect. We also show that, for all levels of polyandry, Mendelian alleles at genetic loci that influence the trade-off between maternal fecundity and offspring viability reach an evolutionary stable state, whereas pairs of reciprocally imprinted alleles do not.
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Evolución Biológica , Impresión Genómica , Interpretación Estadística de Datos , Modelos GenéticosRESUMEN
Imprinted genes exhibit silencing of one of the parental alleles during embryonic development. In a previous study imprinted genes were found to have reduced intron content relative to a non-imprinted control set (Hurst et al., 1996). However, due to the small sample size, it was not possible to analyse the source of this effect. Here, we re-investigate this observation using larger datasets of imprinted and control (non-imprinted) genes that allow us to consider mouse and human, and maternally and paternally silenced, imprinted genes separately. We find that, in the human and mouse, there is reduced intron content in the maternally silenced imprinted genes relative to a non-imprinted control set. Among imprinted genes, a strong bias is also observed in the distribution of intronless genes, which are found exclusively in the maternally silenced dataset. The paternally silenced dataset in the human is not different to the control set; however, the mouse paternally silenced dataset has more introns than the control group. A direct comparison of mouse maternally and paternally silenced imprinted gene datasets shows that they differ significantly with respect to a variety of intron-related parameters. We discuss a variety of possible explanations for our observations.
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This case study of an clinic in California reveals how difficult it can be to successfully integrate traditional medicine with alternative therapies. Take a look at the obstacles that must be overcome.