Fluoride in drinking water and osteosarcoma incidence rates in the continental United States among children and adolescents

IntroductionIt has been suggested that fluoride in drinking water may increase the risk of osteosarcoma in children and adolescents, although the evidence is inconclusive. We investigated the association between community water fluoridation (CWF) and osteosarcoma in childhood and adolescence in the continental U.S.MethodsWe used the cumulative osteosarcoma incidence rate data from the CDC Wonder database for 1999–2006, categorized by age group, sex and states. States were categorized as low (≤30%) or high (≥85%) according to the percentage of the population receiving CWF between 1992 and 2006. Confidence intervals for the incidence rates were calculated using the Gamma distribution and the incidence rates were compared between groups using Poisson regression models.ResultsWe found no sex-specific statistical differences in the national incidence rates in the younger groups (5–9, 10–14), although 15–19 males were at higher risk to osteosarcoma than females in the same age group (p < 0.001). Sex and age group specific incidence rates were similar in both CWF state categories. The higher incidence rates among 15–19 year old males vs females was not associated with the state fluoridation status. We also compared sex and age specific osteosarcoma incidence rates cumulated from 1973 to 2007 from the SEER 9 Cancer Registries for single age groups from 5 to 19. There were no statistical differences between sexes for 5–14 year old children although incidence rates for single age groups for 15–19 year old males were significantly higher than for females.ConclusionOur ecological analysis suggests that the water fluoridation status in the continental U.S. has no influence on osteosarcoma incidence rates during childhood and adolescence.     

Rational targeting of population groups and residential areas for colorectal cancer screening

BackgroundSociodemographic and spatial disparities in incidence and mortality burden of colorectal cancer (CRC) are important to consider in the implementation of population screening, in order to achieve expected benefit and not increase health inequities. Analytic methods should be adapted to provide rational support for targeted interventions.MethodsCRC incidence rates by tumor stage (I-IV) and location (colon vs. rectum) were analyzed for the time period 2008–2016 within a screening-relevant age interval of 55–74 years for the population of South and West Sweden, where screening is planned for. The study population was stratified by sex, country of birth, educational level (for Swedish-born citizens) and residential area. We also estimated disparities in excess mortality from CRC across groups of patients accordant to relevant population groups.ResultsThe analyses were based on 8961 patients with a first CRC diagnosis. There were marked socioeconomic gradients in the stage II-IV CRC incidence rates among Swedish-born men and women. Compared to men with high educational level, the incidence rate ratios (IRRs) of stage II, III, and IV CRC in men with low educational level were 1.38 (95% confidence interval 1.18, 1.62), 1.09 (0.95, 1.26), and 1.18 (1.02, 1.37), respectively. In women, the corresponding figures were 1.26 (1.06, 1.51), 1.19 (1.01, 1.39), and 1.45 (1.20, 1.80). The groups of patients with low educational level showed relatively high excess mortality burdens from CRC.ConclusionsOur analytic approach provided rational support for targeted intervention when implementing CRC screening, aiming at optimizing participation in groups with low educational level.     

Cross sectional study of primary care groups in London: association of measures of socioeconomic and health status with hospital admission rates

ObjectivesTo calculate socioeconomic and health status measures for the primary care groups in London and to examine the association between these measures and hospital admission rates.DesignCross sectional study.Setting66 primary care groups in London, total list size 8.0 million people.ResultsStandardised hospital admission ratios varied from 74 to 116 for total admissions and from 50 to 124 for emergency admissions. Directly standardised admission rates for asthma varied from 152 to 801 per 100 000 (mean 364) and for diabetes from 235 to 1034 per 100 000 (mean 538). There were large differences in the mortality, socioeconomic, and general practice characteristics of the primary care groups. Hospital admission rates were significantly correlated with many of the measures of chronic illness and deprivation. The strongest correlations were with disability living allowance (R=0.64 for total admissions and R=0.62 for emergency admissions, P<0.0001). Practice characteristics were less strongly associated with hospital admission rates.ConclusionsIt is feasible to produce a range of socioeconomic, health status, and practice measures for primary care groups for use in needs assessment and in planning and monitoring health services. These measures show that primary care groups have highly variable patient and practice characteristics and that hospital admission rates are associated with chronic illness and deprivation. These variations will need to be taken into account when assessing performance.     

Randomised controlled trial of effect of feedback on general practitioners' prescribing in Australia

ObjectiveTo evaluate the effect on general practitioners’ prescribing of feedback on their levels of prescribing. DesignRandomised controlled trial.SettingGeneral practice in rural Australia.Participants2440 full time recognised general practitioners practising in non-urban areas.InterventionTwo sets of graphical displays (6 months apart) of their prescribing rates for 2 years, relative to those of their peers, were posted to participants. Data were provided for five main drug groups and were accompanied by educational newsletters. The control group received no information on their prescribing.ResultsThe intervention and control groups had similar baseline characteristics (age, sex, patient mix, practices). Median prescribing rates for the two groups were almost identical before and after the interventions. Any changes in prescribing observed in the intervention group were also seen in the control group. There was no evidence that feedback reduced the variability in prescribing nor did it differentially affect the very high or very low prescribers. ConclusionsThe form of feedback evaluated here—mailed, unsolicited, centralised, government sponsored, and based on aggregate data—had no impact on the prescribing levels of general practitioners.

Key messages

• Feedback of prescribing data to general practitioners is widely practised by government agencies
• The belief is that this will lead to reduced variability and lower rates of prescribing of key drugs, but this has not been tested in randomised trials
• In a large randomised trial Australian general practitioners received feedback comprising simple graphical displays of their prescribing data for five key groups of drugs
• This had no impact on the level or variability of subsequent prescribing rates
• Unsolicited, centralised, government sponsored feedback based on aggregate data had no impact on the prescribing levels of general practitioners

     

两种不同手术方式治疗恶性梗阻性黄疸患者的临床疗效比较研究

目的:探讨经皮肝穿刺胆管引流术(PTCD)与经内镜逆行胰胆管造影术(ERCP)治疗恶性梗阻性黄疸的治疗效果,并进行比较分析。方法:选取2016年1月~2018年5月期间我院收治的127例恶性梗阻性黄疸患者。根据治疗术式的不同将患者分为ERCP组(n=63,采用ERCP联合金属支架置入术进行治疗)和PTCD组(n=64,采用PTCD进行治疗),比较两组患者术后5d黄疸缓解率,比较两组患者术前、术后2周肝功能指标[血清总胆红素(TBIL)、丙氨酸转氨酶(ALT)、直接胆红素(DBIL)],比较两组患者术后舒适度量表评分情况及并发症发生情况。结果:两组患者术后黄疸总缓解率比较差异无统计学意义(P0.05);PTCD组低位梗阻患者黄疸缓解率低于ERCP组,而高位梗阻患者黄疸缓解率高于ERCP组(P0.05)。两组患者术前、术后2周TBIL、ALT、DBIL比较差异无统计学意义(P0.05);两组患者术后2周TBIL、ALT、DBIL水平较术前比较均下降(P0.05)。ERCP组患者术后舒适度量表评分总分低于PTCD组,差异有统计学意义(P0.05)。PTCD组术后并发症总发生率14.06%(9/64),低于ERCP组的41.27%(26/63)(P0.05)。结论:ERCP与PTCD治疗恶性梗阻性黄疸均可改善患者肝脏功能、疗效满意,但ERCP对低位梗阻患者治疗效果优于PTCD,且术后舒适度优于PTCD,但术后并发症较多,临床应根据患者情况选择具体术式。     

贯穿式胰管空肠黏膜缝合在胰十二指肠切除术中的对比研究

目的:比较贯穿式胰管空肠黏膜缝合与传统缝合方式用于胰十二指肠切除术(PD)中的效果,并分析其用于PD术中的价值。方法:收集2010年9月-2015年12月我院行PD的60例病人临床资料,按照吻合方法的不同分为2组:贯穿组和传统组,各30例。贯穿组患者均采用贯穿式胰管空肠黏膜缝合,传统组患者均采取传统缝合的方式。对比两组患者临床一般指标(胰肠吻合时间、术中出血量和术后住院时间)以及围术期并发症(如胰瘘、淋巴漏、胃排空障碍、肺部感染、吻合口出血、腹腔脓肿)等情况,并比较两组再手术率和再入院率。结果:贯穿组胰肠吻合时间、术中出血量和术后住院时间较传统组减少,差异有统计学意义(P0.05)。贯穿组围术期胰瘘发生率为10.00%,显著低于传统组的40.00%,差异有统计学意义(P0.05),贯穿组B级胰瘘发生率显著低于传统组,差异有统计学意义(P0.05)。贯穿组再手术率、再入院率与传统组比较差异无统计学意义(P0.05)。结论:贯穿式胰管空肠黏膜缝有利于PD患者术后恢复,且围术期胰瘘发生率低,不失为一种有效的胰肠吻合方式。     

玻璃化冻存延期回植技术在大面积皮肤撕脱伤中的应用研究

目的:探讨玻璃化冻存延期回植技术用于大面积撕脱皮肤伤的临床效果。方法:选择2015年6月至2018年6月收治的大面积皮肤撕脱伤的患者16例,根据处理方式分为撕脱皮肤玻璃化冻存二期回植组和撕脱皮肤一期回植组,每组8例患者。皮肤冻存后回植前,采用MTT法检测皮肤活力,比较两组皮片回植后的成活率、感染率、平均住院时间。结果:玻璃化冻存组皮肤冻存后平均活力为92.56%±7.20%,皮片成活率为81.74%±5.78%,感染率12.5%,平均住院时间33.13±3.91 d;一期皮肤回植组皮片成活率21.91%±5.28%,感染率100%,平均住院时间47.50±1.93 d。玻璃化皮肤保存组皮片成活率、感染率、平均住院时间均优于一期皮肤回植组(P0.05)。结论:皮肤玻璃化冻存延期回植技术用于无法一期回植皮肤撕脱伤的临床效果较好。     

The high and heterogeneous burden of breast cancer in Hawaii: A unique multiethnic U.S. Population

BackgroundWhile breast cancer incidence and mortality rates differ across racial/ethnic populations in the U.S., little is known about Asian and Pacific Island subpopulations. Hawaii is one of the most racially/ethnically diverse states in the U.S. Overall, Hawaii ranks 5^th highest for breast cancer incidence in the nation (2010–2014) and rates have increased in recent years despite a stable national trend. In contrast, for breast cancer mortality, Hawaii has the 3^rd lowest rate in the nation, with rates demonstrating a steady decline for nearly 3 decades.MethodsWe examined incidence and mortality trends from 1984–2013 across the five major racial/ethnic populations of Hawaii (Native Hawaiian, White, Japanese, Chinese, and Filipino) using Hawaii’s Surveillance, Epidemiology, and End Results (SEER) registry data.ResultsWith the exception of Chinese, all groups experienced increasing incidence over the thirty year period. While Japanese experienced the most pronounced recent increase, with incidence now exceeding that of Whites, their mortality rates have remained low for decades. Native Hawaiians have consistently had the highest incidence and mortality rates in the state. The incidence rates of hormone receptor (HR)-positive breast cancer were higher among Japanese and Native Hawaiians as compared to Whites. Relative to Whites, Native Hawaiians also had a higher incidence rate of the HER2-positive subtype and, Japanese, of the triple-negative (HR-/HER2-) subtype of breast cancer.ConclusionsStudies such as this underscore the importance of considering the heterogeneity in breast cancer rates and subtypes across the different racial/ethnic populations.     

Golden Plover Pluvialis apricaria breeding success on a moor managed for shooting Red Grouse Lagopus lagopus

Capsule The best estimate of breeding success was a mean of 0.57 fledglings per pair, which when combined with adult survival rates, successfully explained the observed population trend.

Aims To quantify Golden Plover breeding success on a moor managed for shooting Red Grouse Lagopus lagopus.

Methods An intensive study recorded the fate of individual Golden Plover nests and, using radiotelemetry, chicks. The factors associated with mortality were examined, allowing the construction of a model of breeding success. Adult survival was estimated from return rates of colour-ringed birds.

Results Estimated rates of daily nest survival during laying (0.8636) were significantly lower than during incubation (0.9913). The daily survival rate of chicks less than nine days (0.8868) was significantly lower than for older chicks (0.9792). A population model based on these parameters overestimated the rate of nest losses, but accurately described brood survival and fledging success. Although predation rates were low, poor survival of young chicks through starvation or exposure suggest other factors were limiting breeding success at the study site.

Conclusions Predation rates of Golden Plover nests and chicks can be low on moorlands managed for shooting Red Grouse. However, in the absence of predation, other factors may still reduce chick survival and limit breeding success.     

Ecological study of social fragmentation,poverty, and suicide

ObjectivesTo investigate the association between suicide and area based measures of deprivation and social fragmentation.DesignEcological study.Setting633 parliamentary constituencies of Great Britain as defined in 1991.ResultsMortality from suicide and all other causes increased with increasing Townsend deprivation score, social fragmentation score, and abstention from voting in all age and sex groups. Suicide mortality was most strongly related to social fragmentation, whereas deaths from other causes were more closely associated with Townsend score. Constituencies with absolute increases in social fragmentation and Townsend scores between 1981 and 1991 tended to have greater increases in suicide rates over the same period. The relation between change in social fragmentation and suicide was largely independent of Townsend score, whereas the association with Townsend score was generally reduced after adjustment for social fragmentation.ConclusionsSuicide rates are more strongly associated with measures of social fragmentation than with poverty at a constituency level.

Key messages

• Place of residence may affect health, and mortality from most common diseases tends to be higher in areas characterised by low socioeconomic position
• Research dating back over 100 years suggests that social fragmentation may influencesuicide
• In the 1980s and 1990s, parliamentary constituencies with high levels of social fragmentation had high rates of suicide, independent of deprivation
• Constituencies with the greatest increases in social fragmentation between 1981 and 1991 also had the greatest increases in suicide rates over the same period
• Any targeting of suicide prevention may be more effective if aimed at socially fragmented rather than deprived areas

     

Comparative Efficacy of Vertebroplasty,Kyphoplasty, and Medical Therapy for Vertebral Fractures on Survival and Prevention of Recurrent Fractures

ObjectiveTo evaluate the efficacy of surgical and medical therapies on recurrent vertebral fracture and mortality rates.MethodsA retrospective review of medical records was performed of patients seen at Emory University Spine Center and Hospital (Atlanta, Georgia) for vertebral fracture between 1998 and 2007. Patients with vertebral fracture or who underwent vertebroplasty or kyphoplasty were identified by use of the International Classification of Diseases, Ninth Revision and Current Procedural Terminology codes, respectively. Outcome measures included site and date of recurrent vertebral fractures and mortality.ResultsWe identified 250 patients with vertebral fractures and classified them into 4 groups: surgical therapy only, surgical plus medical treatment, medical therapy only, and no treatment. There was no significant difference in the cumulative survival rates among the 4 study groups nor between the treatment groups. There was, however, a significant difference in the cumulative refracturefree rates among the 4 study groups (P < .0001). Recurrent fracture-free rates were highest in the group that received no treatment. The 2-year cumulative refracture-free rates were 95.9%, 84.8%, 81.7%, and 68.5%, respectively, for the no treatment, medical therapy only, surgical treatment only, and medical plus surgical therapy groups. Recurrent fracture-free rates were significantly different for patients who received surgical or medical or surgical plus medical therapy (P = .0007), with patients in the medical plus surgical group having the shortest time to refracture, although these patients may have been sicker and more frail than the other groups.ConclusionWe found that surgical treatment with vertebroplasty or kyphoplasty did not decrease recurrent vertebral fractures in patients presenting with an initial vertebral fracture. Medical and surgical therapies together may shorten the time to refracture, but the observed elevated risk may be due to other confounding factors. We found no difference in survival in patients undergoing kyphoplasty or vertebroplasty in comparison with medical or no treatment groups. The relationship between surgical and medical therapy and vertebral refracture rates should be further evaluated with use of a prospective cohort design. (Endocr Pract. 2012;18:499-507)     

Probability of lung cancer in a population excluded from screening due to low PLCOM2012 risk

BackgroundSeveral randomized trials demonstrated have reduced lung cancer mortality with screening using computed tomography. However, there remains debate about the optimal approach for determining screening eligibility, and no evidence yet exists reporting lung cancer rates in those excluded from screening due to too low of a personalized risk.MethodsThis study was based on the Alberta Lung Cancer Screening Study, which received 1737 applicants and enrolled 850 based on the NLST criteria or a PLCO_M2012 risk ≥ 1.5%. We excluded 887 applicants who were interested in screening but deemed ineligible. We report lung cancer rates in the screened and unscreened cohorts.ResultsWe observed 30 and 8 lung cancers in the screened and unscreened groups, respectively. Only 1 of 8 lung cancers were among those considered too low risk (0.14%), while the remaining 7 were among those excluded for other reasons, including symptoms requiring more immediate workup. No NLST eligible but PLCO risk < 1.5% screened individual had a lung cancer detected as part of the study, so that of all applicants contacting the program with risk estimates less than 1.5%, only 1/857 (0.12%) developed lung cancer.ConclusionOur findings indicate that a risk-based approach for screening eligibility is unlikely to miss many lung cancers.     

Under-Utilization of Implantable Cardioverter Defibrillators in Patients with Heart Failure - The Current State of Sudden Cardiac Death Prophylaxis

BackgroundDespite ACC/AHA guidelines indicating implantable cardioverter defibrillator (ICD) as class I therapy for primary prevention of sudden cardiac death in patients with EF≤35%, ICD utilization rates in real world practice have been low.ObjectiveTo determine the rate of ICD implantation at a tertiary care academic center and to assess the reasons for under-utilization of the same.MethodsReview of a prospectively collected database which included all patients diagnosed with an EF≤35% was performed to assess the rate of ICD implantation and mortality. Reasons for non-implantation of ICD were then assessed from detailed chart review.ResultsA total of 707 patients (age 69.4 ± 14.1 years) with mean EF of 26±7% were analyzed. Only 28% (200/707) of patients had ICDs implanted. Mortality was lower in the group with ICD (25% vs 37%, p=0.004). When patients who either died or were lost to follow-up prior to 2005 were excluded, ICD utilization rate was still low at 37.6%. The most common reason for non-implantation of ICD was physicians not discussing this option with their patients. Patient refusal was the second most common reason.ConclusionsICD Implantation rates for primary prevention of SCD in patients with EF≤35% is low. Physician and patient education should be addressed to improve the utilization rates.Key words: Implantable cardioverter-defibrillator, Outcomes, sudden cardiac death     

曲妥珠单抗联合SOX方案治疗HER-2阳性晚期胃癌的临床疗效观察

目的:探讨曲妥珠单抗联合替吉奥和奥沙利铂(SOX方案)治疗人类表皮生长因子受体-2(HER-2)阳性晚期胃癌的临床疗效。方法:选择2014年2月到2016年2月在我院收治的48例HER-2阳性晚期胃癌患者,随机分为实验组和对照组,各24例。对照组患者给予SOX化疗方案,实验组患者给予曲妥珠单抗联合SOX化疗方案,两组患者均给予治疗3个疗程。评价并比较两组患者临床疗效。比较两组患者治疗后不良反应发生情况。检测并比较两组患者治疗前后血清糖类抗原125(CA125)、癌胚抗原(CEA)及组织多肽特异性抗原(TPS)水平。结果:实验组患者的有效率(RR)为58.33%、疾病控制率(DCR)为87.50%,均明显高于对照组患者的29.17%和45.83%,差异具有统计学意义(P0.05)。治疗后两组患者血清CA125、CEA及TPS水平均明显低于治疗前,且实验组患者上述各指标均明显低于对照组,差异具有统计学意义(P0.05)。两组患者不良反应发生率比较差异均无统计学意义(P0.05)。结论:曲妥珠单抗联合SOX方案治疗HER-2阳性晚期胃癌患者临床疗效显著,能够明显降低血清CA125、CEA及TPS水平,不良反应发生率低,值得在临床上推广应用。     

Incidental and Non-incidental Papillary Thyroid Microcarcinoma in Denmark 1996–2015: A national study on incidence,outcome and thoughts on active surveillance

BackgroundIncidental and non-incidental papillary microcarcinomas (PMC) are associated with different outcomes and treatment options may vary. The least favourable outcome is typically seen when carcinoma is suspected prior to surgery. Only a few studies have addressed the prognosis based on the way of detection for PMC, and they have been limited to retrospective single-center studies. We hypothesize that the “way of detection” may predict prognosis.The aim was to calculate the incidence and outcome of PMC based on the way of detection and to identify patients that may be suitable for active surveillance.MethodThis national cohort study consists of 803 patients diagnosed with PMC in Denmark from 1996 to 2015. Patients were identified from the DATHYRCA database and allocated into groups according to the way of detection leading to surgery: Incidental at surgery (n = 527), non-incidental with symptoms suspected from the index tumor (n = 134) and non-incidental with symptoms suspected from a metastasis (n = 142).ResultsAge-standardized incidence rates increased from 0.35 per 100,000 per year in 1996 to 1.19 per 100,000 per year in 2015. A significant rise in incidence was found for both the incidental group and non-incidental group with symptoms suspected from a metastasis. Recurrence free survival was significantly worse for patients with suspicion of metastasis prior to surgery than patient groups without. No difference in mortality was found between groups.ConclusionPMC patients without suspicion of metastasis have the same low risk of recurrence as incidental cases and may be candidates for active surveillance.     

Associations between cesarean delivery and child mortality: A national record linkage longitudinal study of 17.8 million births in Brazil

BackgroundThere is an increasing use of cesarean delivery (CD) based on preference rather than on medical indication. However, the extent to which nonmedically indicated CD benefits or harms child survival remains unclear. Our hypothesis was that in groups with a low indication for CD, this procedure would be associated with higher child mortality and in groups with a clear medical indication CD would be associated with improved child survival chances.Methods and findingsWe conducted a population-based cohort study in Brazil by linking routine data on live births between January 1, 2012 and December 31, 2018 and assessing mortality up to 5 years of age. Women with a live birth who contributed records during this period were classified into one of 10 Robson groups based on their pregnancy and delivery characteristics. We used propensity scores to match CD with vaginal deliveries (1:1) and prelabor CD with unscheduled CD (1:1) and estimated associations with child mortality using Cox regressions. A total of 17,838,115 live births were analyzed. After propensity score matching (PSM), we found that live births to women in groups with low expected frequencies of CD (Robson groups 1 to 4) had a higher death rate up to age 5 years if they were born via CD compared with vaginal deliveries (HR = 1.25, 95% CI: 1.22 to 1.28; p < 0.001). The relative rate was greatest in the neonatal period (HR = 1.39, 95% CI: 1.34 to 1.45; p < 0.001). There was no difference in mortality rate when comparing offspring born by a prelabor CD to those born by unscheduled CD. For the live births to women with a CD in a prior pregnancy (Robson group 5), the relative rates for child mortality were similar for those born by CD compared with vaginal deliveries (HR = 1.05, 95% CI: 1.00 to 1.10; p = 0.024). In contrast, for live births to women in groups with high expected rates of CD (Robson groups 6 to 10), the child mortality rate was lower for CD than for vaginal deliveries (HR = 0.90, 95% CI: 0.89 to 0.91; p < 0.001), particularly in the neonatal period (HR = 0.84, 95% CI: 0.83 to 0.85; p < 0.001). Our results should be interpreted with caution in clinical practice, since relevant clinical data on CD indication were not available.ConclusionsIn this study, we observed that in Robson groups with low expected frequencies of CD, this procedure was associated with a 25% increase in child mortality. However, in groups with high expected frequencies of CD, the findings suggest that clinically indicated CD is associated with a reduction in child mortality.

In a study of linked population-based data, Enny Paixao and colleagues study the associations between cesarean section and child mortality among 17.8 million live births in Brazil.     

Open randomised trial of intermittent very low energy diet together with nicotine gum for stopping smoking in women who gained weight in previous attempts to quit

ObjectiveTo determine whether attempts to prevent weight gain will increase success rates for stopping smoking.Design16 week, open, randomised study with 1 year follow up.SettingObesity unit.Subjects287 female smokers who had quit smoking before but started again because of weight concerns.InterventionCombination of a standard smoking cessation programme with nicotine gum and a behavioural weight control programme including a very low energy diet. A control group was treated with the identical programme but without the diet.ResultsAfter 16 weeks, 68/137 (50%) women had stopped smoking in the diet group versus 53/150 (35%) in the control group (P=0.01). Among these women, weight fell by mean 2.1 (95% confidence interval 2.9 to 1.3) kg in the diet group but increased by 1.6 (0.9 to 2.3) kg in the control group (P<0.001). After 1 year the success rates in the diet and control groups were 38/137 (28%) and 24/150 (16%) respectively (P<0.05), but there was no statistical difference in weight gain.ConclusionsCombining the smoking cessation programme with an intervention to control weight helped women to stop smoking and control weight.     

Growth rate, root development and nutrient uptake of 55 plant species from the Great Plains Grasslands, USA

Empirical and theoretical studies have highlighted that plantcompetition and species diversity are substantially affected by interactionsamong plant growth and nutrient uptake rates, root lateral spread, rootplasticity, and small scale soil nutrient heterogeneity. This study wasdesignedto (a) experimentally estimate parameters regarding rootscaling patterns, root biomass allocation, growth rates, nutrient productivity,and root nutrient influx rates of 55 plant species common to Great Plainsgrasslands; and (b) determine if grasses and forbs can beclassified into statistically distinct groups based on these characteristics.Wefound that: (1) In all species root lateral spread, rootlength, and root surface area had significant allometric scaling relationshipswith root biomass, but that the relationships were unaffected by Navailability.(2) Reductions in the supply of N increased the root:shootratio in 62% of the species. (3) The frequency distributionandmean values of maximum relative growth rates were very similar for grasses andforbs/shrubs, but mid successional grasses had a higher relative growth ratethan late successional ones. (4) In 78% of the species tested,N productivity was increased by reductions in the N supply.(5)When subjected to a high N supply, the N and P productivity of grasses was, onaverage, higher than that of forbs/shrubs, and the N and P productivity ofC₄ grasses was, on average, higher than that of C₃grasses. No differences were found under a low N supply. (6)Nodifferences on the average maximum N and P influx rates per unit of rootsurfacearea were found between grasses and forbs or between C₃ andC₄ grasses, but both were correlated with maximum relative growthrate. (7) The set of parameters we measured were able toseparate grasses and forbs/shrubs into statistically distinct groups that tendto follow in broad terms the coarse vs. fine scaleforaging strategies hypothesis.     

Distinct responses of growth and respiration to growth temperatures in two mangrove species

Background and AimsMangrove plants are mostly found in tropical and sub-tropical tidal flats, and their limited distribution may be related to their responses to growth temperatures. However, the mechanisms underlying these responses have not been clarified. Here, we measured the dependencies of the growth parameters and respiration rates of leaves and roots on growth temperatures in typical mangrove species.MethodsWe grew two typical species of Indo-Pacific mangroves, Bruguiera gymnorrhiza and Rhizophora stylosa, at four different temperatures (15, 20, 25 and 30 °C) by irrigating with fresh water containing nutrients, and we measured growth parameters, chemical composition, and leaf and root O₂ respiration rates. We then estimated the construction costs of leaves and roots and the respiration rates required for maintenance and growth.Key ResultsThe relative growth rates of both species increased with growth temperature due to changes in physiological parameters such as net assimilation rate and respiration rate rather than to changes in structural parameters such as leaf area ratio. Both species required a threshold temperature for growth (12.2 °C in B. gymnorrhiza and 18.1 °C in R. stylosa). At the low growth temperature, root nitrogen uptake rate was lower in R. stylosa than in B. gymnorrhiza, leading to a slower growth rate in R. stylosa. This indicates that R. stylosa is more sensitive than B. gymnorrhiza to low temperature.ConclusionsOur results suggest that the mangrove species require a certain warm temperature to ensure respiration rates sufficient for maintenance and growth, particularly in roots. The underground temperature probably limits their growth under the low-temperature condition. The lower sensitivity of B. gymnorrhiza to low temperature shows its potential to adapt to a wider habitat temperature range than R. stylosa. These growth and respiratory features may explain the distribution patterns of the two mangrove species.     

Causes and consequences of crossing-over evidenced via a high-resolution recombinational landscape of the honey bee

BackgroundSocial hymenoptera, the honey bee (Apis mellifera) in particular, have ultra-high crossover rates and a large degree of intra-genomic variation in crossover rates. Aligned with haploid genomics of males, this makes them a potential model for examining the causes and consequences of crossing over. To address why social insects have such high crossing-over rates and the consequences of this, we constructed a high-resolution recombination atlas by sequencing 55 individuals from three colonies with an average marker density of 314 bp/marker.ResultsWe find crossing over to be especially high in proximity to genes upregulated in worker brains, but see no evidence for a coupling with immune-related functioning. We detect only a low rate of non-crossover gene conversion, contrary to current evidence. This is in striking contrast to the ultrahigh crossing-over rate, almost double that previously estimated from lower resolution data. We robustly recover the predicted intragenomic correlations between crossing over and both population level diversity and GC content, which could be best explained as indirect and direct consequences of crossing over, respectively.ConclusionsOur data are consistent with the view that diversification of worker behavior, but not immune function, is a driver of the high crossing-over rate in bees. While we see both high diversity and high GC content associated with high crossing-over rates, our estimate of the low non-crossover rate demonstrates that high non-crossover rates are not a necessary consequence of high recombination rates.

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