焕镛木花部数量变异和腋生花现象

对广西环江木论的焕镛木[Woonyoungia septentrionalis(Dandy)Law]自然居群花朵着生方式和性别比例作了随机抽样调查,首次发现其花的着生方式除多数为顶生花外,还有少量的腋生花,自然居群中雄株与雌株的性别比例为1.21:1,对中国科学院华南植物园栽培居群和广西环江木论自然居群20株600朵花进行的解剖统计揭示,雌、雄花各部分的数量是变化的,雄花的花被片一轮或两轮,2－6片,雄蕊81－152枚,雌花的花被片两轮,外轮2－4片,内轮4－13片,心皮3－8枚,只有雄花花药2室及雌花每心皮具2个胚珠是稳定的。花部表型性状的大幅度变异表明焕镛木具有较丰富的遗传多样性。讨论了生花与顶生花在木兰科系统发育中的意义、表型性状的异步进化现象以及建立焕镛木属Woonyoungia Law的依据。     

长江中下游湿地大型水鸟种群动态和幼鸟比例研究

迁徙水鸟保护对生物多样性保护具有重要意义。开展水鸟种群数量和幼鸟比例监测,对科学评估其种群变化趋势、制定长期保护策略具有重要价值。长江中下游湿地是东亚-澳大利西亚迁徙路线上重要的水鸟越冬区之一。本研究采用野外同步调查等方法对该区域87个湿地的亟需保护和具有代表性的10种大型越冬水鸟,其中雁形目6种,分别是鸿雁Anser cygnoides、豆雁A.fabalis、灰雁A.grus、白额雁A.albifrons、小白额雁A.erythropus和小天鹅Cygnus columbianus;鹤形目4种,分别是白鹤Leucogeranus leucogeranus、白枕鹤Antigone vipio、灰鹤Grus grus和白头鹤G.monacha,进行了长期监测(2003—2019年冬季),并结合相关文献,评估其种群变化趋势、幼鸟比例和死亡率。研究结果如下：(1)2005—2019年3种水鸟(豆雁、灰雁和灰鹤)的种群数量呈上升趋势,7种水鸟(鸿雁、白额雁、小白额雁、小天鹅、白鹤、白枕鹤和白头鹤)种群数量呈下降趋势;(2)种群趋势下降组(N=7)和上升组(N=3)的幼鸟比例均值在2016—2...     

Kappa-chain constant-region gene sequences in genus Rattus: coding regions are diverging more rapidly than noncoding regions

We have determined the nucleotide sequence of a 1,200-base pair (bp) genomic fragment that includes the kappa-chain constant-region gene (C kappa) from two species of native Australian rodents, Rattus leucopus cooktownensis and Rattus colletti. Comparison of these sequences with each other and with other rodent C kappa genes shows three surprising features. First, the coding regions are diverging at a rate severalfold higher than that of the nearby noncoding regions. Second, replacement changes within the coding region are accumulating at a rate at least as great as that of silent changes. Third, most of the amino acid replacements are localized in one region of the C kappa domain--namely, the carboxy-terminal "bends" in the alpha-carbon backbone. These three features have previously been described from comparisons of the two allelic forms of C kappa genes in R. norvegicus. These data imply the existence of considerable evolutionary constraints on the noncoding regions (based on as yet undetermined functions) or powerful positive selection to diversify a portion of the constant-region domain (whose physiological significance is not known). These surprising features of C kappa evolution appear to be characteristic only of closely related C kappa genes, since comparison of rodent with human sequences shows the expected greater conservation of coding regions, as well as a predominance of silent nucleotide substitutions within the coding regions.      

Growth of a Molecular Base for Feeding: The Mind Body Dualism

It is often difficult to identify the ‘who, when, and where’ of advances in medicine and surgery because it's a rare advance indeed (such as the use of digitalis by William Withering) that can be clearly related to the astuteness of one person at one time and place.     

A Hidden Markov Model approach to variation among sites in rate of evolution

The method of Hidden Markov Models is used to allow for unequal and unknown evolutionary rates at different sites in molecular sequences. Rates of evolution at different sites are assumed to be drawn from a set of possible rates, with a finite number of possibilities. The overall likelihood of phylogeny is calculated as a sum of terms, each term being the probability of the data given a particular assignment of rates to sites, times the prior probability of that particular combination of rates. The probabilities of different rate combinations are specified by a stationary Markov chain that assigns rate categories to sites. While there will be a very large number of possible ways of assigning rates to sites, a simple recursive algorithm allows the contributions to the likelihood from all possible combinations of rates to be summed, in a time proportional to the number of different rates at a single site. Thus with three rates, the effort involved is no greater than three times that for a single rate. This "Hidden Markov Model" method allows for rates to differ between sites and for correlations between the rates of neighboring sites. By summing over all possibilities it does not require us to know the rates at individual sites. However, it does not allow for correlation of rates at nonadjacent sites, nor does it allow for a continuous distribution of rates over sites. It is shown how to use the Newton-Raphson method to estimate branch lengths of a phylogeny and to infer from a phylogeny what assignment of rates to sites has the largest posterior probability. An example is given using beta-hemoglobin DNA sequences in eight mammal species; the regions of high and low evolutionary rates are inferred and also the average length of patches of similar rates.      

Associations between Red Cell Polymorphisms and Plasmodium falciparum Infection in the Middle Belt of Ghana

Background

Red blood cell (RBC) polymorphisms are common in malaria endemic regions and are known to protect against severe forms of the disease. Therefore, it is important to screen for these polymorphisms in drugs or vaccines efficacy trials. This study was undertaken to evaluate associations between clinical malaria and RBC polymorphisms to assess biological interactions that may be necessary for consideration when designing clinical trials.

Method

In a cross-sectional study of 341 febrile children less than five years of age, associations between clinical malaria and common RBC polymorphisms including the sickle cell gene and G6PD deficiency was evaluated between November 2008 and June 2009 in the middle belt of Ghana, Kintampo. G6PD deficiency was determined by quantitative methods whiles haemoglobin variants were determined by haemoglobin titan gel electrophoresis. Blood smears were stained with Giemsa and parasite densities were determined microscopically.

Results

The prevalence of clinical malarial among the enrolled children was 31.9%. The frequency of G6PD deficiency was 19.0% and that for the haemoglobin variants were 74.7%, 14.7%, 9.1%, 0.9% respectively for HbAA, HbAC, HbAS and HbSS. In Multivariate regression analysis, children with the HbAS genotype had 79% lower risk of malaria infection compared to those with the HbAA genotypes (OR = 0.21, 95% CI: 0.06–0.73, p = 0.01). HbAC genotype was not significantly associated with malaria infection relative to the HbAA genotype (OR = 0.70, 95% CI: 0.35–1.42, p = 0.33). G6PD deficient subgroup had a marginally increased risk of malaria infection compared to the G6PD normal subgroup (OR = 1.76, 95% CI: 0.98–3.16, p = 0.06).

Conclusion

These results confirm previous findings showing a protective effect of sickle cell trait on clinical malaria infection. However, G6PD deficiency was associated with a marginal increase in susceptibility to clinical malaria compared to children without G6PD deficiency.     

Symbiotic relationships between soil fungi and plants reduce N2O emissions from soil

N₂O is a potent greenhouse gas involved in the destruction of the protective ozone layer in the stratosphere and contributing to global warming. The ecological processes regulating its emissions from soil are still poorly understood. Here, we show that the presence of arbuscular mycorrhizal fungi (AMF), a dominant group of soil fungi, which form symbiotic associations with the majority of land plants and which influence a range of important ecosystem functions, can induce a reduction in N₂O emissions from soil. To test for a functional relationship between AMF and N₂O emissions, we manipulated the abundance of AMF in two independent greenhouse experiments using two different approaches (sterilized and re-inoculated soil and non-mycorrhizal tomato mutants) and two different soils. N₂O emissions were increased by 42 and 33% in microcosms with reduced AMF abundance compared to microcosms with a well-established AMF community, suggesting that AMF regulate N₂O emissions. This could partly be explained by increased N immobilization into microbial or plant biomass, reduced concentrations of mineral soil N as a substrate for N₂O emission and altered water relations. Moreover, the abundance of key genes responsible for N₂O production (nirK) was negatively and for N₂O consumption (nosZ) positively correlated to AMF abundance, indicating that the regulation of N₂O emissions is transmitted by AMF-induced changes in the soil microbial community. Our results suggest that the disruption of the AMF symbiosis through intensification of agricultural practices may further contribute to increased N₂O emissions.     

颈髓损伤的常规MRI表现与DTI技术临床应用

目的：比较不同时期颈髓损伤的MRI表现及DTI的应用价值。方法：收集急性颈髓压迫病例15例、慢性颈髓压迫病例23例、颈髓慢性压迫合并急性压迫病例12例。15例健康志愿者作为对照组。进行常规MRI检查,应用DTI检查测量表现扩散系数（ADC）值和各向异性分数（FA）。比较各组间ADC值和FA值,并进行统计学分析。结果：急性颈髓迫病例,常规MRI显示颈髓增粗,呈等T1长T2信号;慢性颈髓压迫病例,9例呈长T1长T2信号,14例呈等T1长T2信号;慢性颈髓压迫并急性压迫病例颈髓明显增粗,呈等、长T1明显长T2信号。与对照组比较：急性颈髓压迫组的ADC值和FA值均明显降低,两组的差异有显著性;慢性颈髓压迫组的FA值降低,ADC值增高,两组的差异有显著性;慢性脊髓压迫合并急性脊髓压迫组ADC值与对照组比较无差异,FA值低于对照组。颈髓压迫各组间ADC值及FA值比较差异显著。结论：不同时期颈髓损伤常规MRI图像缺乏特异性,根据ADC值及FA值可判断颈髓损伤的时期。     

Retrograde tracing and toe spreading after experimental autologous nerve transplantation and crush injury of the sciatic nerve: a descriptive methodological study

ABSTRACT: Evaluation of functional and structural recovery after peripheral nerve injury is crucial to determine the therapeutic effect of a nerve repair strategy. In the present study, we examined the relationship between the structural evaluation of regeneration by means of retrograde tracing and the functional evaluation analysis of toe spreading. Two standardized rat sciatic nerve injury models were used to address this relationship. As such, animals received either a 2 cm sciatic nerve defect (neurotmesis) followed by autologous nerve transplantation (ANT animals) or a crush injury with spontaneous recovery (axonotmesis; CI animals). Functional recovery of toe spreading was observed over an observation period of 84 days. In contrast to CI animals, ANT animals did not reach pre-surgical levels of toe spreading. After the observation period, the lipophilic dye DiI was applied to label sensory and motor neurons in dorsal root ganglia (DRG; sensory neurons) and spinal cord (motor neurons), respectively. No statistical difference in motor or sensory neuron counts could be detected between ANT and CI animals. In the present study we could indicate that there was no direct relationship between functional recovery (toe spreading) measured by SSI and the number of labelled (motor and sensory) neurons evaluated by retrograde tracing. The present findings demonstrate that a multimodal approach with a variety of independent evaluation tools is essential to understand and estimate the therapeutic benefit of a nerve repair strategy.