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1.
Methods Mol Biol ; 2818: 239-248, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39126479

RESUMO

During meiosis, homologous chromosomes reciprocally exchange segments of DNA via the formation of crossovers. However, the frequency and position of crossover events along chromosomes are not random. Each chromosome must receive at least one crossover, and the formation of a crossover at one location inhibits the formation of additional crossovers nearby. These crossover patterning phenomena are referred to as "crossover assurance" and "crossover interference," respectively. One key method for quantifying meiotic crossover patterning is to immunocytologically measure the position and intensity of crossover-associated protein foci along the length of meiotic prophase I chromosomes. This approach was recently used to map the position of a conserved E3 ligase, HEI10, along Arabidopsis pachytene chromosomes, providing experimental support for a novel mechanistic "coarsening model" for crossover patterning. Here we describe a user-friendly method for automatically measuring the position and intensity of recombination-associated foci along meiotic prophase I chromosomes that is broadly applicable to studies in different eukaryotic species.


Assuntos
Troca Genética , Meiose , Meiose/genética , Arabidopsis/genética , Cromossomos de Plantas/genética , Prófase Meiótica I , Recombinação Genética
2.
Curr Opin Plant Biol ; 81: 102570, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-38838583

RESUMO

Meiosis is a conserved eukaryotic cell division that produces spores required for sexual reproduction. During meiosis, chromosomes pair and undergo programmed DNA double-strand breaks, followed by homologous repair that can result in reciprocal crossovers. Crossover formation is highly regulated with typically few events per homolog pair. Crossovers additionally show wider spacing than expected from uniformly random placement - defining the phenomenon of interference. In plants, the conserved HEI10 E3 ligase is initially loaded along meiotic chromosomes, before maturing into a small number of foci, corresponding to crossover locations. We review the coarsening model that explains these dynamics as a diffusion and aggregation process, resulting in approximately evenly spaced HEI10 foci. We review how underlying chromatin states, and the presence of interhomolog polymorphisms, shape the meiotic recombination landscape, in light of the coarsening model. Finally, we consider future directions to understand the control of meiotic recombination in plant genomes.


Assuntos
Cromatina , Meiose , Meiose/genética , Cromatina/genética , Cromatina/metabolismo , Recombinação Genética/genética , Troca Genética , Polimorfismo Genético , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas/genética , Cromossomos de Plantas/genética
3.
Nat Plants ; 10(3): 453-468, 2024 03.
Artigo em Inglês | MEDLINE | ID: mdl-38379086

RESUMO

Meiosis is a specialized eukaryotic division that produces genetically diverse gametes for sexual reproduction. During meiosis, homologous chromosomes pair and undergo reciprocal exchanges, called crossovers, which recombine genetic variation. Meiotic crossovers are stringently controlled with at least one obligate exchange forming per chromosome pair, while closely spaced crossovers are inhibited by interference. In Arabidopsis, crossover positions can be explained by a diffusion-mediated coarsening model, in which large, approximately evenly spaced foci of the pro-crossover E3 ligase HEI10 grow at the expense of smaller, closely spaced clusters. However, the mechanisms that control HEI10 dynamics during meiosis remain unclear. Here, through a forward genetic screen in Arabidopsis, we identified high crossover rate3 (hcr3), a dominant-negative mutant that reduces crossover interference and increases crossovers genome-wide. HCR3 encodes J3, a co-chaperone related to HSP40, which acts to target protein aggregates and biomolecular condensates to the disassembly chaperone HSP70, thereby promoting proteasomal degradation. Consistently, we show that a network of HCR3 and HSP70 chaperones facilitates proteolysis of HEI10, thereby regulating interference and the recombination landscape. These results reveal a new role for the HSP40/J3-HSP70 chaperones in regulating chromosome-wide dynamics of recombination via control of HEI10 proteolysis.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Troca Genética , Proteólise , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Meiose
4.
Elife ; 122023 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-36847348

RESUMO

The shuffling of genetic material facilitated by meiotic crossovers is a critical driver of genetic variation. Therefore, the number and positions of crossover events must be carefully controlled. In Arabidopsis, an obligate crossover and repression of nearby crossovers on each chromosome pair are abolished in mutants that lack the synaptonemal complex (SC), a conserved protein scaffold. We use mathematical modelling and quantitative super-resolution microscopy to explore and mechanistically explain meiotic crossover pattering in Arabidopsis lines with full, incomplete, or abolished synapsis. For zyp1 mutants, which lack an SC, we develop a coarsening model in which crossover precursors globally compete for a limited pool of the pro-crossover factor HEI10, with dynamic HEI10 exchange mediated through the nucleoplasm. We demonstrate that this model is capable of quantitatively reproducing and predicting zyp1 experimental crossover patterning and HEI10 foci intensity data. Additionally, we find that a model combining both SC- and nucleoplasm-mediated coarsening can explain crossover patterning in wild-type Arabidopsis and in pch2 mutants, which display partial synapsis. Together, our results reveal that regulation of crossover patterning in wild-type Arabidopsis and SC-defective mutants likely acts through the same underlying coarsening mechanism, differing only in the spatial compartments through which the pro-crossover factor diffuses.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Complexo Sinaptonêmico/genética , Troca Genética , Arabidopsis/genética , Meiose , Pareamento Cromossômico , Adenosina Trifosfatases/genética , Proteínas de Arabidopsis/genética
5.
Curr Top Dev Biol ; 151: 91-126, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36681479

RESUMO

Chromosomes adopt specific conformations to regulate various cellular processes. A well-documented chromosome configuration is the highly compacted chromosome structure during metaphase. More regional chromatin conformations have also been reported, including topologically associated domains encompassing mega-bases of DNA and local chromatin loops formed by kilo-bases of DNA. In this review, we discuss the changes in chromatin conformation taking place between somatic and meiotic cells, with a special focus on the establishment of a proteinaceous structure, called the chromosome axis, at the beginning of meiosis. The chromosome axis is essential to support key meiotic processes such as chromosome pairing, homologous recombination, and balanced chromosome segregation to transition from a diploid to a haploid stage. We review the role of the chromosome axis in meiotic chromatin organization and provide a detailed description of its protein composition. We also review the conserved and distinct roles between species of axis proteins in meiotic recombination, which is a major factor contributing to the creation of genetic diversity and genome evolution. Finally, we discuss situations where the chromosome axis is deregulated and evaluate the effects on genome integrity and the consequences from protein deregulation in meiocytes exposed to heat stress, and aberrant expression of genes encoding axis proteins in mammalian somatic cells associated with certain types of cancers.


Assuntos
Neoplasias , Complexo Sinaptonêmico , Animais , Meiose/genética , Pareamento Cromossômico , Cromatina/genética , Neoplasias/genética , Mamíferos/genética
6.
PLoS Genet ; 18(7): e1010304, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35830475

RESUMO

Genome duplication, which leads to polyploidy, poses challenges to the meiotic segregation of the now-multiple homologous chromosome copies. Genome scan data showed previously that adaptation to polyploid meiosis in autotetraploid Arabidopsis arenosa is likely multigenic, involving genes encoding interacting proteins. But what does this really mean? Functional follow-up studies to genome scans for multigenic traits remain rare in most systems, and thus many mysteries remain about the "functional architecture" of polygenic adaptations. Do different genes all contribute subtle and additive progression towards a fitness optimum, or are there more complex interactions? We previously showed that derived alleles of genes encoding two interacting meiotic axis proteins (ASY1 and ASY3) have additive functional consequences for meiotic adaptation. Here we study derived versus ancestral alleles of the meiotic cohesin subunit REC8, which has roles in chromatin condensation, recruiting the axes, and other critical functions in meiosis. We use genetic and cytological approaches to assess the functional effects of REC8 diploid versus tetraploid alleles, as well as their interaction with ancestral versus derived alleles of ASY1 and ASY3. We show that homozygotes for derived (tetraploid) REC8 alleles have significantly fewer unpaired univalents, a common problem in neotetraploids. Interactions with ASY1 and ASY3 are complex, with the genes in some cases affecting distinct traits, and additive or even antagonistic effects on others. These findings suggest that the road to meiotic adaptation in A. arenosa was perhaps neither straight nor smooth.


Assuntos
Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona , Segregação de Cromossomos , Humanos , Meiose/genética , Poliploidia , Tetraploidia , Coesinas
7.
J Sci Med Sport ; 25(3): 216-221, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34740516

RESUMO

OBJECTIVES: In one English Premier League football club over four seasons, 1) describe the number of hamstring strain injuries (HSI) sustained using the British Athletics Muscle Injury Classification (BAMIC); 2) determine if intramuscular tendon HSI influenced the time to return to play (TTRTP) and reinjury rate; 3) determine the predictors of TTRTP and reinjury. DESIGN: Retrospective cohort design. METHODS: All first team players who sustained a HSI between 2014 and 2018 were included. Players underwent an MRI scan that was graded by a Radiologist using the BAMIC (0a-4) criteria. TTRTP, reinjury rate and information on suspected predictors were recorded. RESULTS: Thirty-five HSI experienced by 24 players (age = 26 ±â€¯4 years) were recorded over the 4 seasons. There was a difference in TTRTP between grades 1a and 2c (P = 0.007), but not between 2b and 2c (P = 0.845). Grade of HSI (P ≤ 0.001) and removal of the player (P < 0.001) were predictors of TTRTP, with each increase in grade resulting in an additional 3 days of TTRTP, and being removed, an additional 11 days. Grade and all other predictors did not influence reinjury rate, albeit higher odds were evident for previous HSI, experiencing the HSI during sprinting, passing a ball or stretching, and reported increase days of pain during walking. CONCLUSIONS: HSIs extending into the intramuscular tendon (2b cf. 2c) did not influence TTRTP or re-injury, albeit TTRTP was affected by the BAMIC grade and if the player was removed from activity.


Assuntos
Traumatismos em Atletas , Músculos Isquiossurais , Relesões , Adulto , Estudos de Coortes , Músculos Isquiossurais/diagnóstico por imagem , Músculos Isquiossurais/lesões , Humanos , Estudos Retrospectivos , Volta ao Esporte , Tendões , Adulto Jovem
8.
Curr Biol ; 31(21): 4713-4726.e4, 2021 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-34480856

RESUMO

Polyploidy is a major driver of evolutionary change. Autopolyploids, which arise by within-species whole-genome duplication, carry multiple nearly identical copies of each chromosome. This presents an existential challenge to sexual reproduction. Meiotic chromosome segregation requires formation of DNA crossovers (COs) between two homologous chromosomes. How can this outcome be achieved when more than two essentially equivalent partners are available? We addressed this question by comparing diploid, neo-autotetraploid, and established autotetraploid Arabidopsis arenosa using new approaches for analysis of meiotic CO patterns in polyploids. We discover that crossover interference, the classical process responsible for patterning of COs in diploid meiosis, is defective in the neo-autotetraploid but robust in the established autotetraploid. The presented findings suggest that, initially, diploid-like interference fails to act effectively on multivalent pairing and accompanying pre-CO recombination interactions and that stable autopolyploid meiosis can emerge by evolution of a "supercharged" interference process, which can now act effectively on such configurations. Thus, the basic interference mechanism responsible for simplifying CO patterns along chromosomes in diploid meiosis has evolved the capability to also simplify CO patterns among chromosomes in autopolyploids, thereby promoting bivalent formation. We further show that evolution of stable autotetraploidy preadapts meiosis to higher ploidy, which in turn has interesting mechanistic and evolutionary implications.


Assuntos
Arabidopsis , Arabidopsis/genética , Segregação de Cromossomos/genética , Diploide , Meiose/genética , Poliploidia
9.
Nat Commun ; 12(1): 4674, 2021 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-34344879

RESUMO

In most organisms, the number and distribution of crossovers that occur during meiosis are tightly controlled. All chromosomes must receive at least one 'obligatory crossover' and crossovers are prevented from occurring near one another by 'crossover interference'. However, the mechanistic basis of this phenomenon of crossover interference has remained mostly mysterious. Using quantitative super-resolution cytogenetics and mathematical modelling, we investigate crossover positioning in the Arabidopsis thaliana wild-type, an over-expressor of the conserved E3 ligase HEI10, and a hei10 heterozygous line. We show that crossover positions can be explained by a predictive, diffusion-mediated coarsening model, in which large, approximately evenly-spaced HEI10 foci grow at the expense of smaller, closely-spaced clusters. We propose this coarsening process explains many aspects of Arabidopsis crossover positioning, including crossover interference. Consistent with this model, we also demonstrate that crossover positioning can be predictably modified in vivo simply by altering HEI10 dosage, with higher and lower dosage leading to weaker and stronger crossover interference, respectively. As HEI10 is a conserved member of the RING finger protein family that functions in the interference-sensitive pathway for crossover formation, we anticipate that similar mechanisms may regulate crossover positioning in diverse eukaryotes.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas Cromossômicas não Histona/metabolismo , Troca Genética/genética , Meiose/genética , Proteínas de Arabidopsis/genética , Proteínas Cromossômicas não Histona/genética , Cromossomos de Plantas/genética , Cromossomos de Plantas/metabolismo , Simulação por Computador , Dosagem de Genes , Estágio Paquíteno/genética , Complexo Sinaptonêmico/genética , Complexo Sinaptonêmico/metabolismo
10.
BMJ Open Sport Exerc Med ; 6(1): e000683, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32405430

RESUMO

OBJECTIVE: To investigate the influence of trunk and lower limb motion on electromyography (EMG) muscle activity and recruitment patterns around the shoulder. DESIGN: Systematic review. DATA SOURCES: MEDLINE, CINAHL, PEDro, AMED, PubMed, Cochrane Central Register of Controlled trials, Cochrane Database of Systematic reviews, SportsDiscuss and PROSPERO. ELIGIBILITY CRITERIA: Studies investigating both multiregional kinetic chain (KC) shoulder exercises and localised non-kinetic chain (nKC) shoulder exercises in healthy subjects under the same experimental conditions were included in this review. RESULTS: KC exercises produced greater EMG activation levels in 5 of 11 studies for the lower trapezius. Of the remaining studies, five found no difference between the exercise types and one favoured nKC exercises. KC exercises produced greater EMG activation levels in 5 of 11 studies for the serratus anterior. Of the remaining studies, three reported the opposite and three found no significant difference between the exercise types. nKC exercises produced greater EMG activation in infraspinatus in three of four studies. KC exercises produced the lowest trapezius muscle ratios in all studies. Studies investigating the upper trapezius, middle trapezius, supraspinatus, subscapularis, biceps brachii, latifissimus dorsi, pectoralis major, deltoid, and trapezius and serratus anterior ratios showed inconsistency. CONCLUSION: This review found evidence that integrating the KC during shoulder rehabilitation may increase axioscapular muscle recruitment, produce lower trapezius muscle ratios and reduce the demands on the rotator cuff. Stepping appears preferable to squatting. PROSPERO REGISTRATION NUMBER: CRD42015032557, 2015.

11.
Proc Natl Acad Sci U S A ; 117(16): 8980-8988, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32273390

RESUMO

Polyploidy, which results from whole genome duplication (WGD), has shaped the long-term evolution of eukaryotic genomes in all kingdoms. Polyploidy is also implicated in adaptation, domestication, and speciation. Yet when WGD newly occurs, the resulting neopolyploids face numerous challenges. A particularly pernicious problem is the segregation of multiple chromosome copies in meiosis. Evolution can overcome this challenge, likely through modification of chromosome pairing and recombination to prevent deleterious multivalent chromosome associations, but the molecular basis of this remains mysterious. We study mechanisms underlying evolutionary stabilization of polyploid meiosis using Arabidopsis arenosa, a relative of A. thaliana with natural diploid and meiotically stable autotetraploid populations. Here we investigate the effects of ancestral (diploid) versus derived (tetraploid) alleles of two genes, ASY1 and ASY3, that were among several meiosis genes under selection in the tetraploid lineage. These genes encode interacting proteins critical for formation of meiotic chromosome axes, long linear multiprotein structures that form along sister chromatids in meiosis and are essential for recombination, chromosome segregation, and fertility. We show that derived alleles of both genes are associated with changes in meiosis, including reduced formation of multichromosome associations, reduced axis length, and a tendency to more rod-shaped bivalents in metaphase I. Thus, we conclude that ASY1 and ASY3 are components of a larger multigenic solution to polyploid meiosis in which individual genes have subtle effects. Our results are relevant for understanding polyploid evolution and more generally for understanding how meiotic traits can evolve when faced with challenges.


Assuntos
Arabidopsis/genética , Produtos Agrícolas/genética , Genoma de Planta , Meiose/genética , Tetraploidia , Alelos , Proteínas de Arabidopsis/genética , Segregação de Cromossomos , Produção Agrícola , Proteínas de Ligação a DNA/genética , Evolução Molecular , Loci Gênicos , Técnicas de Genotipagem , Família Multigênica
12.
Methods Mol Biol ; 2061: 37-46, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31583651

RESUMO

Arabidopsis arenosa has recently become established as a model organism for investigating how meiosis has evolved to overcome the meiotic challenges faced by newly formed autotetraploids. Here, we describe a protocol for the preparation of spread, immunolabeled prophase I chromosomes from established A. arenosa autotetraploids for imaging with three-dimensional structured illumination microscopy (3D-SIM). This technique allows us to dissect the unique synaptic behavior in A. arenosa and identify synaptic partner switch sites that are unresolvable with conventional widefield microscopy.


Assuntos
Arabidopsis/genética , Análise Citogenética , Meiose , Microscopia , Poliploidia , Cromossomos de Plantas , Análise Citogenética/métodos , Imageamento Tridimensional , Microscopia/métodos
13.
Plant J ; 100(4): 754-767, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31369173

RESUMO

S-Acylation is a reversible post-translational lipid modification in which a long chain fatty acid covalently attaches to specific cysteine(s) of proteins via a thioester bond. It enhances the hydrophobicity of proteins, contributes to their membrane association and plays roles in protein trafficking, stability and signalling. A family of Protein S-Acyl Transferases (PATs) is responsible for this reaction. PATs are multi-pass transmembrane proteins that possess a catalytic Asp-His-His-Cys cysteine-rich domain (DHHC-CRD). In Arabidopsis, there are currently 24 such PATs, five having been characterized, revealing their important roles in growth, development, senescence and stress responses. Here, we report the functional characterization of another PAT, AtPAT21, demonstrating the roles it plays in Arabidopsis sexual reproduction. Loss-of-function mutation by T-DNA insertion in AtPAT21 results in the complete failure of seed production. Detailed studies revealed that the sterility of the mutant is caused by defects in both male and female sporogenesis and gametogenesis. To determine if the sterility observed in atpat21-1 was caused by upstream defects in meiosis, we assessed meiotic progression in pollen mother cells and found massive chromosome fragmentation and the absence of synapsis in the initial stages of meiosis. Interestingly, the fragmentation phenotype was substantially reduced in atpat21-1 spo11-1 double mutants, indicating that AtPAT21 is required for repair, but not for the formation, of SPO11-induced meiotic DNA double-stranded breaks (DSBs) in Arabidopsis. Our data highlight the importance of protein S-acylation in the early meiotic stages that lead to the development of male and female sporophytic reproductive structures and associated gametophytes in Arabidopsis.


Assuntos
Aciltransferases/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Óvulo Vegetal/fisiologia , Pólen/fisiologia , Acilação , Aciltransferases/química , Aciltransferases/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Membrana Celular/metabolismo , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Regulação da Expressão Gênica de Plantas , Meiose , Mutação , Plantas Geneticamente Modificadas , Polinização
14.
Wellcome Open Res ; 4: 53, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-32030356

RESUMO

Background: Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis and bacterial vaginosis have been associated with preterm birth and low birth weight, and are highly prevalent among pregnant women in many low- and middle-income settings. There is conflicting evidence on the potential benefits of screening and treating these infections in pregnancy. Newly available diagnostic technologies make it possible, for the first time, to conduct definitive field trials to fill this knowledge gap. The primary aim of this study is to evaluate whether antenatal point-of-care testing and immediate treatment of these curable sexually transmitted and genital infections (STIs) leads to reduction in preterm birth and low birth weight. Methods: The Women and Newborn Trial of Antenatal Interventions and Management (WANTAIM) is a cluster-randomised crossover trial in Papua New Guinea to compare point-of-care STI testing and immediate treatment with standard antenatal care (which includes the WHO-endorsed STI 'syndromic' management strategy based on clinical features alone without laboratory confirmation). The unit of randomisation is a primary health care facility and its catchment communities. The primary outcome is a composite measure of two events: the proportion of women and their newborns in each trial arm, who experience either preterm birth (delivery <37 completed weeks of gestation as determined by ultrasound) and/or low birth weight (<2500 g measured within 72 hours of birth). The trial will also evaluate neonatal outcomes, as well as the cost-effectiveness, acceptability and health system requirements of this strategy, compared with standard care. Conclusions: WANTAIM is the first randomised trial to evaluate the effectiveness, cost-effectiveness, acceptability and health system requirements of point-of-care STI testing and treatment to improve birth outcomes in high-burden settings. If the intervention is proven to have an impact, the trial will hasten access to these technologies and could improve maternal and neonatal health in high-burden settings worldwide. Registration: ISRCTN37134032.

15.
Am J Cardiovasc Dis ; 8(2): 14-18, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29755836

RESUMO

BACKGROUND AND AIMS: Low serum 25-OH D levels are associated with increased cardiovascular morbidity and mortality. Recent studies have linked 25-OH D deficiency with the presence of CAD. Women, especially post-menopausal, tend to suffer from accelerated atherosclerosis, along with vitamin D deficiency. In the present study we sought to investigate whether there is a direct association of coronary artery luminal stenosis with 25-OH D deficiency in women. PATIENTS AND METHODS: We enrolled women aged >40 who were scheduled to undergo elective coronary angiography between 3/2011 and 10/2016 in a prospective observational study. RESULTS: We included a total of 105 women. Patients had hypertension (73%), hyperlipidemia (54%), diabetes (29%), smoking (31%), family history of CAD (62%), and known CAD (21%). Median 25-OH D levels were 15.8 ng/mL (range, 3.9-79). Patients had left-anterior descending (31%), left circumflex (22%), and right coronary artery disease (26%); 27% had 2-vessel and 11% had 3-vessel disease. There was a significant inverse correlation between 25-OH D levels and the degree of maximum luminal stenosis. The burden of CAD increased across categories of worsening 25-OH D deficiency. CONCLUSIONS: Vitamin D deficiency is associated with the degree of luminal stenosis and burden of CAD in women undergoing coronary angiography. Future studies should investigate if the repletion of 25-OH D impacts the progression of CAD and cardiovascular mortality.

16.
Genetics ; 208(4): 1409-1420, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29496746

RESUMO

Meiotic recombination shuffles genetic information from sexual species into gametes to create novel combinations in offspring. Thus, recombination is an important factor in inheritance, adaptation, and responses to selection. However, recombination is not a static parameter; meiotic recombination rate is sensitive to variation in the environment, especially temperature. That recombination rates change in response to both increases and decreases in temperature was reported in Drosophila a century ago, and since then in several other species. But it is still unclear what the underlying mechanism is, and whether low- and high-temperature effects are mechanistically equivalent. Here, we show that, as in Drosophila, both high and low temperatures increase meiotic crossovers in Arabidopsis thaliana We show that, from a nadir at 18°, both lower and higher temperatures increase recombination through additional class I (interfering) crossovers. However, the increase in crossovers at high and low temperatures appears to be mechanistically at least somewhat distinct, as they differ in their association with the DNA repair protein MLH1. We also find that, in contrast to what has been reported in barley, synaptonemal complex length is negatively correlated with temperature; thus, an increase in chromosome axis length may account for increased crossovers at low temperature in A. thaliana, but cannot explain the increased crossovers observed at high temperature. The plasticity of recombination has important implications for evolution and breeding, and also for the interpretation of observations of recombination rate variation among natural populations.


Assuntos
Adaptação Biológica/genética , Arabidopsis/genética , Meiose/genética , Recombinação Genética , Temperatura , Arabidopsis/metabolismo , Troca Genética , Modelos Biológicos
17.
Int J Clin Pract ; 71(6)2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28544081

RESUMO

AIMS: Hypoglycaemia in patients with diabetes can be induced by insulins and sulfonylureas. We assessed the real-world impact of specific monotherapy and combination regimens on hypoglycaemic events requiring hospitalisation and related secondary costs to the English healthcare system. METHODS: This retrospective observational study used the Clinical Practice Research Datalink with linked hospital admission data during 2008-2012. Patients with type 2 diabetes mellitus (T2DM) using antihyperglycaemic agents (AHAs) were assigned to mutually exclusive subgroups (insulin- and non-insulin-containing regimens; treatment groups of interest; age group) based on treatment at index date (date of first AHA prescription). Outcomes were number and cost of hospital admissions with hypoglycaemic event-related diagnosis codes. RESULTS: We identified 110 206 patients with T2DM (mean age 64.9 years, time since diagnosis 5.4 years, HbA1c at index 7.4%), with 439 hypoglycaemic events requiring inpatient hospitalisation (mean length of stay 6.3 days, mean cost/stay £1351). Event rates and cost of stay were highest in patients treated with sulfonylurea- or insulin-based regimens. Event rates, duration and cost of stay were higher in older patients. CONCLUSION: Rates of severe hypoglycaemic events varied substantially between T2DM regimens. In this study of patients treated in clinical practice in England, sulfonylurea- and insulin-based regimens were associated with the highest event rates and costs associated with hospitalisation for severe hypoglycaemic events; hospitalisation for severe hypoglycaemic events was not observed with dipeptidyl peptidase-4 inhibitor monotherapy or with metformin.


Assuntos
Diabetes Mellitus Tipo 2/economia , Custos de Cuidados de Saúde , Hipoglicemia/economia , Adulto , Idoso , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/tratamento farmacológico , Inglaterra , Feminino , Hospitalização/economia , Humanos , Hipoglicemia/induzido quimicamente , Hipoglicemia/tratamento farmacológico , Hipoglicemiantes/economia , Hipoglicemiantes/uso terapêutico , Insulina/economia , Insulina/uso terapêutico , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Compostos de Sulfonilureia/economia , Compostos de Sulfonilureia/uso terapêutico
18.
PLoS One ; 12(3): e0173407, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28282433

RESUMO

OBJECTIVE: To describe the cause-specific morbidity and mortality, and referral patterns of all neonates admitted to a tertiary referral hospital in the northern provinces of Vietnam. DESIGN: A prospective hospital based observational study. SETTING: The Neonatal Department, National Hospital of Pediatrics, Hanoi, Vietnam. PATIENTS: All admissions to the Neonatal Department over a 12 month period. MAIN OUTCOME MEASURES: Cause-specific morbidity and mortality; deaths. RESULTS: There were 5064 admissions with the commonest discharge diagnoses being infection (32%) and prematurity (29%). The case fatality ratio (CFR) was 13.9% (n = 703). Infection (38%), cardio/respiratory disorders (27%), congenital abnormalities (20%) and neurological conditions (10%) were the main causes of death. Of all the deaths, 38% had an admission weight ≥2500g. Higher CFR were associated with lower admission weights. Very few deaths (3%) occurred in the first 24 hours of life. Most referrals and deaths came from Hanoi and neighbouring provincial hospitals, with few from the most distant provinces. Two distant referral provinces had the highest CFR. CONCLUSIONS: The CFR was high and few deaths occurred in neonates <24 hours old. The high rates of infection call for an improvement in infection control practices and peripartum antibiotic use at provincial and tertiary level. Understanding provincial hospital capacity and referral pathways is crucial to improving the outcomes at tertiary centres. A quality of care audit tool would enable more targeted interventions and monitoring of health outcomes.


Assuntos
Causas de Morte , Mortalidade Infantil , Morbidade , Doenças Cardiovasculares/epidemiologia , Doenças Cardiovasculares/mortalidade , Anormalidades Congênitas/epidemiologia , Anormalidades Congênitas/mortalidade , Feminino , Hospitalização , Humanos , Lactente , Recém-Nascido , Recém-Nascido Prematuro , Infecções/diagnóstico , Infecções/epidemiologia , Infecções/mortalidade , Masculino , Estudos Prospectivos , Centros de Atenção Terciária , Vietnã
19.
Shoulder Elbow ; 8(4): 279-86, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27660661

RESUMO

BACKGROUND: Advances in arthroscopic surgery have resulted in biomechanically stronger repairs that might allow for accelerated rehabilitation protocols and hence faster return to play. Evidence for such regimes in the shoulder, particularly in elite athletes, is lacking. METHODS: This prospective single surgeon (PB) series included 34 professional footballers undergoing an accelerated rehabilitation programme following arthroscopic soft tissue stabilization subsequent to traumatic anterior shoulder dislocation. Data were collected on time to regain elevation range, external rotation range, return to play and rate of recurrence. RESULTS: Mean follow-up time was 4.8 years (range 2 years to 10 years). Full range of forward elevation was regained at a mean of 5 weeks (range 3 weeks to 7 weeks) and external rotation range (in neutral) at a mean of 6 weeks (range 4 weeks to 8 weeks). Mean return to play time was 11 weeks (range 9 weeks to 14 weeks). Three players (9%) reported a recurrent episode of dislocation at a mean of 19 months. CONCLUSIONS: An accelerated rehabilitation programme resulted in a return to play time of 11 weeks compared to previously reported times of between 5 months and 9 months in the contact sports population. A recurrence rate of 9% compares favourably to other published studies following similar surgery (5.1% to 28.6%) but which employed more conservative postoperative rehabilitation regimes.

20.
BMC Infect Dis ; 16: 250, 2016 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-27268218

RESUMO

BACKGROUND: Sexually transmitted and genital infections in pregnancy are associated with an increased risk of adverse maternal and neonatal health outcomes. High prevalences of sexually transmitted infections have been identified among antenatal attenders in Papua New Guinea. Papua New Guinea has amongst the highest neonatal mortality rates worldwide, with preterm birth and low birth weight major contributors to neonatal mortality. The overall aim of our study was to determine if a novel point-of-care testing and treatment strategy for the sexually transmitted and genital infections Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), Trichomonas vaginalis (TV) and Bacterial vaginosis (BV) in pregnancy is feasible in the high-burden, low-income setting of Papua New Guinea. METHODS: Women attending their first antenatal clinic visit were invited to participate. CT/NG and TV were tested using the GeneXpert platform (Cepheid, USA), and BV tested using BVBlue (Gryphus Diagnostics, USA). Participants received same-day test results and antibiotic treatment as indicated. Routine antenatal care including HIV and syphilis screening were provided. RESULTS: Point-of-care testing was provided to 125/222 (56 %) of women attending routine antenatal care during the three-month study period. Among the 125 women enrolled, the prevalence of CT was 20.0 %; NG, 11.2 %; TV, 37.6 %; and BV, 17.6 %. Over half (67/125, 53.6 %) of women had one or more of these infections. Most women were asymptomatic (71.6 %; 47/67). Women aged 24 years and under were more likely to have one or more STI compared with older women (odds ratio 2.38; 95 % CI: 1.09, 5.21). Most women with an STI received treatment on the same day (83.6 %; 56/67). HIV prevalence was 1.6 % and active syphilis 4.0 %. CONCLUSION: Point-of-care STI testing and treatment using a combination of novel, newly-available assays was feasible during routine antenatal care in this setting. This strategy has not previously been evaluated in any setting and offers the potential to transform STI management in pregnancy and to prevent their associated adverse health outcomes.


Assuntos
Infecções por Chlamydia/diagnóstico , Gonorreia/diagnóstico , Testes Imediatos , Complicações Infecciosas na Gravidez/diagnóstico , Infecções Sexualmente Transmissíveis/diagnóstico , Tricomoníase/diagnóstico , Vaginose Bacteriana/diagnóstico , Adolescente , Adulto , Fatores Etários , Instituições de Assistência Ambulatorial , Infecções Assintomáticas/epidemiologia , Infecções por Chlamydia/epidemiologia , Chlamydia trachomatis , Estudos de Viabilidade , Feminino , Gonorreia/epidemiologia , Infecções por HIV/diagnóstico , Infecções por HIV/epidemiologia , Humanos , Neisseria gonorrhoeae , Razão de Chances , Papua Nova Guiné/epidemiologia , Gravidez , Complicações Infecciosas na Gravidez/epidemiologia , Cuidado Pré-Natal , Prevalência , Infecções Sexualmente Transmissíveis/epidemiologia , Sífilis/diagnóstico , Sífilis/epidemiologia , Tricomoníase/epidemiologia , Trichomonas vaginalis , Vaginose Bacteriana/epidemiologia , Adulto Jovem
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