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3.
J Hosp Infect ; 131: 23-33, 2023 Jan.
Article in English | MEDLINE | ID: mdl-36240955

ABSTRACT

BACKGROUND: Hospital transmission of SARS-CoV-2 has proved difficult to control, with healthcare-associated infections troublesome throughout. AIM: To understand factors contributing to hospital transmission of infections, which is necessary for containing spread. METHODS: An outbreak of 56 staff and patient cases of COVID-19 over a 31-day period in a tertiary referral unit is presented, with at least a further 29 cases identified outside of the unit and the hospital by whole genome sequencing (WGS). FINDINGS: Transmission is documented from staff to staff, staff to patients, and patients to staff, showing disruption of a tertiary referral service, despite implementation of nationally recommended control measures, superior ventilation, and use of personal protective equipment. There was extensive spread from the index case, despite this patient spending only 10 h bed bound on the ward in strict cubicle isolation and with an initial single target low level (CT = 32) polymerase chain reaction test. CONCLUSION: This investigation highlights how effectively and rapidly SARS-CoV-2 can spread in certain circumstances. It raises questions about infection control measures in place at the time and calls into question the premise that transmissibility can be reliably detected by using lower sensitivity rapid antigen lateral flow tests. We also highlight the value of early intervention in reducing impact as well as the value of WGS in understanding outbreaks.


Subject(s)
COVID-19 , Cross Infection , Disease Outbreaks , Disease Transmission, Infectious , SARS-CoV-2 , Humans , COVID-19/diagnosis , COVID-19/prevention & control , COVID-19/transmission , Disease Outbreaks/prevention & control , Hospitals , Infection Control/methods , SARS-CoV-2/genetics , Whole Genome Sequencing , Cross Infection/genetics , Cross Infection/prevention & control , Cross Infection/transmission , Disease Transmission, Infectious/prevention & control
4.
Int J Health Policy Manag ; 12: 7898, 2023.
Article in English | MEDLINE | ID: mdl-38618774

ABSTRACT

This paper responds to lessons from the Adolescent and Youth Health Policy (AYHP) process in South Africa by drawing comparisons with youth participation within the climate justice movement. Relationship building is essential to successful youth participation in health policy and climate change as it creates intergenerational learning and cross-cultural engagement. At the same time, both sets of youth also deal with compounding challenges due to contemporary and historical legacies of colonialism and inequality. Yet, tokenism challenges the participatory process as adults profess to value youth perspectives, yet recommendations by youth often do not get incorporated into policies or plans. For organizations and agencies trying to build youth's capacity, organizations and agencies should look to programs that train youth in advocacy. These programs help build youth's confidence, increase their optimism for change, and give youth a sense of ownership.


Subject(s)
Health Policy , Learning , Adult , Adolescent , Humans , South Africa , Social Justice
7.
Ir Med J ; 112(4): 911, 2019 04 11.
Article in English | MEDLINE | ID: mdl-31241278

ABSTRACT

Aim Proton pump inhibitors (PPIs) are frequently prescribed to surgical patients (50-60%) to prevent gastrointestinal bleeding. However, most surgical patients are at low risk of significant bleeds. The aim of this audit was to identify inappropriate PPI prescribing, if any, in a cohort of surgical inpatients. Methods This was a prospective analysis completed over a 4 month period. Data was collected via review of clinical notes and drug charts. The audit standard was the consensus guideline on indications for PPI use issued by Scarpignato et al (2016). Results In total 89 patients were included (n = 89). 73% were on PPI therapy. 30% had a documented indication for therapy which was concordant with recommendations. However, the majority of PPI prescriptions (70%) were inappropriate. Conclusion PPIs are frequently prescribed to surgical patients without an appropriate indication. Indiscriminate use of these drugs has implications in the form of costs and potential complications.


Subject(s)
Patient Safety , Prescriptions , Proton Pump Inhibitors/administration & dosage , Female , Humans , Male , Prospective Studies , Risk
8.
Ann R Coll Surg Engl ; 101(4): 268-272, 2019 Apr.
Article in English | MEDLINE | ID: mdl-30855173

ABSTRACT

INTRODUCTION: Although close radial margins after breast-conserving surgery routinely undergo re-excision, appropriate management of patients with close anterior margins remains a topic of controversy. An increasing body of literature suggests that re-excision of close anterior margins yields low rates of residual malignancy and may only be necessary in selected patients. The aim of this study was to examine the management of close anterior margins after breast conserving surgery in a single institution and to analyse the rate of residual disease in re-excised anterior margins. METHODS: All patients having breast conserving surgery at St Vincent's University Hospital from January 2008 to December 2012 were reviewed retrospectively. Data collected included patient demographics, tumour characteristics, margin positivity, re-excision rates and definitive histology of the re-excision specimens. A close margin was defined as les than 2 mm. RESULTS: A total of 930 patients were included with an average age of 65 years (range 29-94 years). Of these, 121 (13%) had a close anterior margin. Further re-excison of the anterior margin was carried out in 37 patients (30.6%) and a further 16 (13.2%) proceeded to mastectomy. Residual disease was found in 18.5% (7/36) of those who underwent re-excision and 7/16 (43.75%) of those who underwent mastectomy. Overall, 11.57% (14/121) of patients with close anterior margins were subsequently found to have residual disease. CONCLUSION: The low yield of residual disease in re-excised anterior margins specimens supports the concept that routine re-excision of close anterior margins is not necessary. Further research is required to definitively assess its influence on the risk of local recurrence.


Subject(s)
Margins of Excision , Mastectomy, Segmental , Adult , Aged , Aged, 80 and over , Breast Neoplasms/surgery , Female , Humans , Mastectomy, Segmental/methods , Middle Aged , Reoperation , Retrospective Studies
9.
Ir Med J ; 111(2): 687, 2018 Feb 09.
Article in English | MEDLINE | ID: mdl-29952436

ABSTRACT

Ureteric stents are frequently inserted post endourological procedures. However, subsequent endoscopic stent removal requires a second procedure for the patient and the availability of necessary resources. Longer duration of indwelling stents can lead to increased risk of symptoms and complications. The use of magnetic stents removed with a magnetic retrieval device (BlackStar©), offers an alternative which obviates the need for cystoscopy. We assessed the outcomes for this novel method of stent removal in our institution. A retrospective analysis was performed of all patients undergoing magnetic stent insertion and subsequent removal in a nurse-led clinic over a nine-month period. Patients were followed up with a prospective validated Ureteral Stent Symptoms Questionnaire (USSQ)3. A cost analysis was also performed. In total, 59 patients were treated using magnetic stents. The complication rate was low (6.7%). The median duration of indwelling stent was 5.8 days (range 1-11 days). Patients reported haematuria and lower urinary tract symptoms but >90% experienced no functional impairment with minimal days of employment lost (mean 0.75 days). All patients reported satisfaction with nurse-led stent removal and 97% were happy to have stents removed via this method in the future. The total financial savings were estimated at €47,790 over this period. Nurse-led removal of magnetic stents is safe and well tolerated by patients and enables expedient stent removal. It also provides a significant cost benefit and frees up valuable endoscopic resources.


Subject(s)
Device Removal/methods , Practice Patterns, Nurses' , Stents , Ureter , Device Removal/economics , Device Removal/instrumentation , Humans , Magnetics/instrumentation , Practice Patterns, Nurses'/economics , Prospective Studies , Retrospective Studies , Surveys and Questionnaires , Time Factors
10.
Int J Surg Case Rep ; 16: 64-6, 2015.
Article in English | MEDLINE | ID: mdl-26432498

ABSTRACT

INTRODUCTION: Whilst inherited medullary thyroid cancer has been extensively reported, familial non-medullary thyroid cancer is a rare and less well described clinical entity. Familial forms of the disease demonstrate more aggressive features than sporadic non-medullary thyroid cancer. PRESENTATION OF CASE: A 54 year old lady was referred with globus on a background of a longstanding goitre. Three first degree relatives had a history of non-medullary thyroid carcinoma. Investigations revealed a papillary thyroid carcinoma and the patient proceeded to total thyroidectomy and ipsilateral Level VI neck dissection, followed by adjuvant radioiodine ablation. DISCUSSION: Familial papillary thyroid carcinoma syndrome is defined as three or more first degree relatives diagnosed with the disease in the absence of other known associated syndromes. It is often associated with the presence of benign thyroid disorders, and is characterised by the early onset of multi-focal bilateral locally advanced tumours. CONCLUSION: Familial papillary thyroid cancer is a rare clinical entity but should be considered where ≥3 first degree relatives are diagnosed with non-medullary thyroid cancer. It is necessary to exclude other familial tumour syndromes to make the diagnosis. It demonstrates more aggressive features with higher rates of local recurrence than its sporadic counterpart, and therefore mandates more aggressive management than might otherwise be indicated. Screening of first degree relatives should be considered. SUMMARY: The case of a 54 year old female diagnosed with familial non-medullary thyroid carcinoma is reported.

11.
QJM ; 108(4): 307-14, 2015 Apr.
Article in English | MEDLINE | ID: mdl-25239761

ABSTRACT

BACKGROUND: A number of studies have demonstrated the presence of a diabetic cardiomyopathy, increasing the risk of heart failure development in this population. Improvements in present-day risk factor control may have modified the risk of diabetes-associated cardiomyopathy. AIM: We sought to determine the contemporary impact of diabetes mellitus (DM) on the prevalence of cardiomyopathy in at-risk patients with and without adjustment for risk factor control. DESIGN: A cross-sectional study in a population at risk for heart failure. METHODS: Those with diabetes were compared to those with other cardiovascular risk factors, unmatched, matched for age and gender and then matched for age, gender, body mass index, systolic blood pressure and low density lipoprotein cholesterol. RESULTS: In total, 1399 patients enrolled in the St Vincent's Screening to Prevent Heart Failure (STOP-HF) cohort were included. About 543 participants had an established history of DM. In the whole sample, Stage B heart failure (asymptomatic cardiomyopathy) was not found more frequently among the diabetic cohort compared to those without diabetes [113 (20.8%) vs. 154 (18.0%), P = 0.22], even when matched for age and gender. When controlling for these risk factors and risk factor control Stage B was found to be more prevalent in those with diabetes [88 (22.2%)] compared to those without diabetes [65 (16.4%), P = 0.048]. CONCLUSION: In this cohort of patients with established risk factors for Stage B heart failure superior risk factor management among the diabetic population appears to dilute the independent diabetic insult to left ventricular structure and function, underlining the importance and benefit of effective risk factor control in this population on cardiovascular outcomes.


Subject(s)
Diabetic Cardiomyopathies/prevention & control , Heart Failure/prevention & control , Aged , Cross-Sectional Studies , Diabetic Cardiomyopathies/diagnostic imaging , Diabetic Cardiomyopathies/epidemiology , Diabetic Cardiomyopathies/etiology , Disease Management , Echocardiography, Doppler/methods , Female , Heart Failure/diagnostic imaging , Heart Failure/epidemiology , Heart Failure/etiology , Humans , Ireland/epidemiology , Male , Middle Aged , Risk Factors
12.
J Neuroendocrinol ; 25(7): 644-54, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23631684

ABSTRACT

Individuals integrate information about their environment into adaptive behavioural responses, yet how different sensory modalities contribute to these decisions and where in the brain this integration occurs is not well understood. We presented male cichlid fish (Astatotilapia burtoni) with sensory information in three social contexts: intruder challenge, reproductive opportunity and a socially neutral situation. We then measured behavioural and hormonal responses along with induction of the immediate early gene c-Fos in candidate forebrain regions. In the intruder challenge context, males were exposed to either a visual stimulus of a dominant male, the putative male pheromone androstenedione, or both. We found that, compared to the neutral context, a visual stimulus was necessary and sufficient for an aggressive response, whereas both chemical and visual stimuli were needed for an androgen response. In the reproductive opportunity context, males were exposed to either a visual stimulus of a receptive female, a progesterone metabolite (female pheromone) only, or both. We further found that the visual stimulus is necessary and sufficient for an androgen response in the reproductive opportunity context. In the brain, we observed c-Fos induction in response to a visual challenge stimulus specifically in dopaminergic neurones of area Vc (the central region of the ventral telencephalon), a putative striatal homologue, whereas presentation of a chemical stimulus did not induce c-Fos induction in the intruder challenge context. Our results suggest that different sensory cues are processed in a social context-specific manner as part of adaptive decision-making processes.


Subject(s)
Behavior, Animal , Cichlids/physiology , Neuroendocrine Cells/physiology , Social Environment , Animals , Female , Male
13.
Genes Brain Behav ; 11(7): 813-8, 2012 Oct.
Article in English | MEDLINE | ID: mdl-22862958

ABSTRACT

Sex steroid hormones coordinate neurotransmitter systems in the male brain to facilitate sexual behavior. Although neurotransmitter release in the male brain has been well documented, little is known about how androgens orchestrate changes in gene expression of neurotransmitter receptors. We used male whiptail lizards (Cnemidophorus inornatus) to investigate how androgens alter neurotransmitter-related gene expression in brain regions involved in social decision making. We focused on three neurotransmitter systems involved in male-typical sexual behavior, including the N-methyl-d-aspartate (NMDA) glutamate receptor, nitric oxide and dopamine receptors. Here, we show that in androgen-treated males, there are coordinated changes in neurotransmitter-related gene expression. In androgen-implanted castrates compared with blank-implanted castrates (control group), we found associated increases in neuronal nitric oxide synthase gene expression in the nucleus accumbens (NAcc), preoptic area and ventromedial hypothalamus, a decrease of NR1 gene expression (obligate subunit of NMDA receptors) in the medial amygdaloid area and NAcc and a decrease in D1 and D2 dopamine receptor gene expression in the NAcc. Our results support and expand the current model of androgen-mediated gene expression changes of neurotransmitter-related systems that facilitate sexual behavior in males. This also suggests that the proposed evolutionarily ancient reward system that reinforces sexual behavior in amniote vertebrates extends to reptiles.


Subject(s)
Androgens/pharmacology , Gene Expression Regulation/drug effects , Lizards/genetics , Nitric Oxide Synthase/genetics , Receptors, Dopamine/genetics , Receptors, N-Methyl-D-Aspartate/genetics , Animals , Hypothalamus/metabolism , Lizards/metabolism , Male , Nitric Oxide Synthase/metabolism , Orchiectomy , Receptors, Dopamine/metabolism , Receptors, N-Methyl-D-Aspartate/metabolism , Sexual Behavior, Animal/drug effects
14.
J Neuroendocrinol ; 23(3): 244-53, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21126273

ABSTRACT

The evolution of neuroendocrine mechanisms governing sex-typical behaviour is poorly understood. An outstanding animal model is the whiptail lizard (Cnemidophorus) because both the ancestral and descendent species still exist. The ancestral little striped whiptail, Cnemidophorus inornatus, consists of males and females, which exhibit sex-specific mating behaviours. The descendent desert grassland whiptail, Cnemidophorus uniparens, consists only of females that alternately exhibit both female-like and male-like pseudosexual behaviour. Castrated male C. inornatus will mount a conspecific in response to exogenous androgen, although some are also sensitive to progesterone. This polymorphism in progesterone sensitivity in the ancestral species may have been involved in evolution of progesterone-mediated male-typical behaviour in the descendant unisexual lizards. We tested whether progesterone activates a typically androgenic signalling pathway by investigating hormonal regulation of neuronal nitric oxide synthase (nNOS) using in situ hybridisation and NADPH diaphorase histochemistry, a stain for nNOS protein. NADPH diaphorase is widely distributed throughout the brain of both species, although only in the periventricular nucleus of the preoptic area (pvPOA) are there differences between mounting and non-mounting individuals. The number of cells expressing nNOS mRNA and NADPH diaphorase is higher in the pvPOA of individuals that mount in response to progesterone or androgen. Furthermore, the nNOS promoter has both androgen and progesterone response elements, and NADPH diaphorase colocalises with the progesterone receptor in the pvPOA. These data suggest that a polymorphism in progesterone sensitivity in the sexual ancestor reflects a differential regulation of nNOS and may account for the male-typical behaviour in unisexual whiptail lizards.


Subject(s)
Biological Evolution , Lizards/physiology , Nitric Oxide Synthase Type I/genetics , Parthenogenesis/genetics , Sexual Behavior, Animal/physiology , Animals , Cloning, Molecular , Estrous Cycle/genetics , Estrous Cycle/metabolism , Estrous Cycle/physiology , Female , Gender Identity , Lizards/genetics , Lizards/metabolism , Male , Models, Biological , Nitric Oxide Synthase Type I/metabolism , Nitric Oxide Synthase Type I/physiology , Ovary/metabolism , Parthenogenesis/physiology , Receptors, Progesterone/genetics , Receptors, Progesterone/metabolism , Sex Characteristics , Tissue Distribution
15.
Anaesth Intensive Care ; 38(3): 445-51, 2010 May.
Article in English | MEDLINE | ID: mdl-20514951

ABSTRACT

This study evaluated whether perioperative administration of gabapentin in cardiac surgery patients could reduce postoperative opioid consumption, postoperative sleep or perceived quality of recovery. This randomised controlled trial assigned 60 patients undergoing cardiac surgery to receive 1200 mg of gabapentin or placebo two hours preoperatively, and then 600 mg of gabapentin or placebo twice a day for the next two postoperative days. Postoperative opioid use was measured by the amount of fentanyl used in the first 48 hours postoperatively. Pain at rest and with movement at 12, 24, 48 and 72 hours after surgery, sleep scores on postoperative days two and three and patient-perceived quality of recovery were also assessed. Fentanyl use, visual analog pain scores, sleep scores, adjunctive pain medication use and number of anti-emetics given were not significantly different between the gabapentin and placebo groups. The incidence of side-effects was similar between the gabapentin and placebo groups, and no difference was found between groups in relation to quality of recovery. These findings indicate that preoperative use of gabapentin followed by postoperative dosing for two days did not significantly affect the postoperative pain, sleep, opioid consumption or patient-perceived quality of recovery for patients undergoing cardiac surgery.


Subject(s)
Amines/therapeutic use , Analgesics/therapeutic use , Cardiac Surgical Procedures , Cyclohexanecarboxylic Acids/therapeutic use , Pain, Postoperative/drug therapy , gamma-Aminobutyric Acid/therapeutic use , Adult , Aged , Cardiopulmonary Bypass , Double-Blind Method , Female , Gabapentin , Humans , Male , Middle Aged , Placebos/therapeutic use
16.
Med Vet Entomol ; 22(3): 228-37, 2008 Sep.
Article in English | MEDLINE | ID: mdl-18816271

ABSTRACT

Two experiments were undertaken to estimate the transmission rates of bluetongue virus (BTV) serotype 1 between a biting midge vector, Culicoides sonorensis (Wirth & Jones) (Ceratopogonidae), and a natural host, sheep. In an experiment to measure the transmission rate from vector to host (V-->H), six batches of one, five and 20 intrathoracically infected midges were fed on a total of 18 bluetongue (BT)-naïve sheep. The sheep were then monitored for 21 days for clinical signs of BT, viraemia and antibody response. All sheep fed on by five or 20 midges and five of six sheep fed on by just one midge showed signs of BT, were viraemic and developed antibody. The sixth sheep fed on by a single infected midge did not show signs of BT or have detectable viraemia; it did, however, develop a weak antibody response. A bite from a single infected midge is therefore able to transmit BTV to naïve sheep with 80-100% efficiency. Sheep fed upon by larger numbers of infected midges took less time to reach maximum viraemia and developed stronger antibody responses. Sheep exposed to greater amounts of BTV in feeding midges developed a higher level of viraemia and stronger antibody responses. In a second experiment to measure the transmission rate from host to vector (H-->V), batches of up to 500 uninfected female C. sonorensis fed every 1-2 days on two experimentally infected sheep during the course of infection. Of 3929 engorged midges that were individually titrated after surviving the extrinsic incubation period, only 23 (0.6%) were infected with BTV. Viraemia in the sheep extended for up to 19 days post-inoculation. No infected midges, however, were detected from 14 days post-infection.


Subject(s)
Bluetongue/transmission , Bluetongue/virology , Ceratopogonidae/virology , Animals , Bites and Stings , Female , Insect Vectors , Sheep , Temperature , Viremia , Virus Replication
17.
Heredity (Edinb) ; 97(6): 418-26, 2006 Dec.
Article in English | MEDLINE | ID: mdl-16912700

ABSTRACT

We studied the mating system of white spruce (Picea glauca) in a landscape fragmented by agriculture in northern Ontario, Canada. We sampled 23 stands that ranged in size from 1 to >500 trees isolated by 250-3000 m from the nearest other stand. Six polymorphic allozyme loci from four enzyme systems were used to genotype approximately 10 000 embryos from 104 families. We detected no allele frequency heterogeneity in the pollen pool among stands or families (Phi(FT)=-0.025). Overall, estimates of outcrossing were high (t(m)=94% and mean t(s)=91%) but significantly different from unity. Bi-parental inbreeding (t(m)-t(s)=3.2%) was low but significantly different from zero. Allozyme-based outcrossing estimates did not differ significantly among three stand-size classes (SSCs): small (<10 trees), medium (10-100 trees) and large (> or =100 trees). The number of effective pollen donors was high in all SSCs, but was significantly lower in small stands (N(ep)=62.5) than in medium-sized and large stands (both N(ep)=143). The primary selfing rate was significantly higher in medium stands than in large stands. We found no significant difference in genetic diversity measures in the filial (seed) population among SSCs. Overall, these results indicate that white spruce stands in this fragmented landscape are resistant to genetic diversity losses, primarily through high pollen-mediated gene-flow and early selection against inbred embryos. We discuss the importance of using seed data, in conjunction with genetic data, to evaluate the impacts of fragmentation on natural populations.


Subject(s)
Conservation of Natural Resources , Crosses, Genetic , Gene Flow , Genetic Variation , Picea/genetics , Canada , Gene Frequency , Genetics, Population , Genotype , Pollen
18.
J Matern Fetal Neonatal Med ; 17(2): 139-43, 2005 Feb.
Article in English | MEDLINE | ID: mdl-16076623

ABSTRACT

BACKGROUND: Audit is important in ensuring adequate use of resources and maintaining optimum standards of care. Most of the emphasis in neonatal audit is focused on very low birth weight infants. However, term and near-term infants account for a significant proportion of the workload in neonatal units and warrant regular audit. In addition, audit of these infants may be useful as a marker of the organisation of the perinatal service. METHODS: A retrospective audit was performed of all infants with birth weights greater than or equal to 2,500 grams admitted to the neonatal department in the first week of life over a two-year period, examining mode of delivery, level of care, duration of stay, diagnosis and short-term outcome. RESULTS: Eight hundred and seventy infants were admitted greater than or equal to 2,500 grams birth weight, 54% of all neonatal admissions, during the study period. Six hundred and eighty seven of these infants were admitted in the first week of life and were included in the study; this was 5.8% of infants born with a birth weight 2500 grams or more. Infants born by caesarean section were twice as likely to require admission (9.8%) compared with infants born by vaginal delivery (4.5%). The median length of stay was 3 days (3 hours to 45 days). One hundred and six (15.4%) infants required level 1 or level 2 care. One hundred and eleven infants received normal care, only. Most of these infants were admitted for maternal or social reasons. Other common reasons for admission were jaundice, respiratory disease, neonatal abstinence syndrome and congenital abnormality. Forty-one infants required transfer to another hospital, most commonly for surgical or cardiac conditions. Six infants died after admission. However, only one normally formed infant delivered in our hospital died prior to discharge or transfer. One infant was born at home and four infants who had a lethal congenital abnormality are known to have died following transfer. CONCLUSION: Term and near-term infants account for a significant proportion of neonatal admissions and deserve regular audit. Many admissions are potentially avoidable. Survival for infants weighing 2,500 grams or greater is excellent. Only one normally formed infant died following admission during the study period. The number of "social" admissions of "well" infants highlighted by this study reflects poorly on the services available for well infant whose mothers are unable to care for them for whatever reason. We recommend regular audit of these infants in order to ensure efficient use of neonatal resources and to ensure optimum levels of neonatal intensive care.


Subject(s)
Birth Weight , Intensive Care Units, Neonatal/statistics & numerical data , Workload/statistics & numerical data , Female , Humans , Infant, Newborn , Infant, Newborn, Diseases/therapy , Male , Medical Audit , Perinatal Care , Retrospective Studies , Treatment Outcome
19.
Heredity (Edinb) ; 93(5): 443-9, 2004 Nov.
Article in English | MEDLINE | ID: mdl-15266296

ABSTRACT

Western redcedar (Thuja plicata, Cupressaceae) is a self-fertile conifer with a mixed mating system and significant variation for outcrossing among populations. In this paper, we conducted a fine-scale study of mating system variation to identify correlates of outcrossing in natural populations. We examined variation for outcrossing within and among individual trees, and describe a new method to estimate outcrossing using bulked DNA samples. Bulking (assaying DNA tissues from several individuals simultaneously) increases the experimental power without increasing the experimental effort. We sampled 80 trees from four natural populations in southwestern British Columbia. From each tree, we sampled from up to six crown positions (three heights and inner vs outer branches). From each position, two samples of three seedlings each were bulked before DNA extractions. Using four microsatellite loci, we obtained outcrossing rates for each tree and for each of the six crown positions. We found individual tree selfing rates to increase with tree height in all four populations, but selfing rates did not differ among crown positions. The higher selfing rate of larger trees is probably due to their greater proportional contribution to local pollen clouds. Individual tree outcrossing rates ranged from 22 to 100% and the population outcrossing rates from 66 to 78%. Missed alleles due to bulking and the estimation method used both cause a downward bias in outcrossing rates, so that these estimates are probably lower than the actual outcrossing rates. Nevertheless, the trends we observed are not affected by systematic biases of estimation.


Subject(s)
Cedrus/genetics , Crosses, Genetic , DNA, Plant/analysis , Genes, Plant/genetics , Genetic Variation , Microsatellite Repeats/genetics , Cedrus/chemistry
20.
J Hered ; 95(2): 172-6, 2004.
Article in English | MEDLINE | ID: mdl-15073234

ABSTRACT

A per-generation somatic mutation rate for microsatellites was estimated in western redcedar (Thuja plicata, Donn ex D. Don.: Cupressaceae). A total of 80 trees representative of the average size and age of reproductive trees were sampled in four natural populations in southwestern British Columbia. Samples of bulked haploid megagametophytes were collected from two or three positions on each tree, assuming that the collections were far enough apart that the same mutant sector was not sampled twice. All samples were genotyped at eight microsatellite loci. A single mutation corresponding to a stepwise increase in one dinucleotide repeat was detected. The estimated mutation rate for microsatellites was 6.3 x 10(-4) mutations per locus per generation (or 3.1 x 10(-4) per allele per generation), with a 95% confidence interval of 3.0 x 10(-5) to 4.0 x 10(-3) mutations per locus. Somatic mutations can contribute to a greater mutational load in trees, as compared to shorter lived plants, and genotypic mosaics within an individual have important implications for plant defense strategies and plant evolution.


Subject(s)
Evolution, Molecular , Microsatellite Repeats/genetics , Mutation/genetics , Seeds , Thuja/genetics , Alleles , British Columbia , Trees
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