Analysis of quantitative trait loci affecting chlorophyll content of rice leaves in a double haploid population and two backcross populations

Chlorophyll content, one of the most important physiological parameters related to plant photosynthesis, is usually used to predict yield potential. To map the quantitative trait loci (QTLs) underlying the chlorophyll content of rice leaves, a double haploid (DH) population was developed from an indica/japonica (Zhenshan 97/Wuyujing 2) crossing and two backcross populations were established subsequently by backcrossing DH lines with each of their parents. The contents of chlorophyll a and chlorophyll b were determined by using a spectrophotometer to directly measure the leaf chlorophyll extracts. To determine the leaf chlorophyll retention along with maturation, all measurements were performed on the day of heading and were repeated 30 days later. A total of 60 QTLs were resolved for all the traits using these three populations. These QTLs were distributed on 10 rice chromosomes, except chromosomes 5 and 10; the closer the traits, the more clustering of the QTLs residing on common rice chromosomal regions. In general, the majority of QTLs that specify chlorophyll a content also play a role in determining chlorophyll b content. Strangely, chlorophyll content in this study was found mostly to be lacking or to have a negative correlation with yield. In both backcross F₁ populations, overdominant (or underdominant) loci were more important than complete or partially dominant loci for main-effect QTLs and epistatic QTLs, thereby supporting previous findings that overdominant effects are the primary genetic basis for depression in inbreeding and heterosis in rice.     

不同光强下生长的两种榕树叶片光合能力与比叶重、氮含量及分配的关系

观测了不同光强下生长的两种榕树幼苗叶片的光合能力、比叶重(LMA)、氮含量及在光合机构中的分配.结果表明,两种榕树幼苗的最大净光合速率(Pmax)均随生长光强的升高而升高,这与LMA、单位面积氮含量(NA)和光合氮利用效率随生长光强的升高而升高有关.除36%光强下外,相同光强下生长的喜光的斜叶榕(Ficus tinctoria)的Pmax均显著高于耐荫的假斜叶榕(Ficus subulata),这与其叶片中氮在羧化组份和生物力能学组份中的分配系数、LMA和NA较高有关.     

Crystallographic study of the iron-sulfur flavoprotein trimethylamine dehydrogenase from the bacterium W3A1

Large single crystals of trimethylamine dehydrogenase, containing both [4Fe-4S]²⁺ centers and covalently bound FMN, have been prepared by the macro seeding technique. The crystals are monoclinic, space group P2₁ with cell parameters $\text{a = 147.63}\text{A}\text{?}\text{, b = 71.96}\text{A}\text{?}\text{, c = 83.66}\text{A}\text{?}\text{and}\text{β = 97.64 °}$, and diffract to at least 2.0 Å resolution. There is one dimer of approximately 166,000 M_m per asymmetric unit. A 5.0 Å resolution anomalous scattering difference Patterson has been computed which shows the presence and position of two [4Fe-4S]²⁺ centers in the asymmetric unit. A self-rotation function computed at 6.0 Å resolution indicates a non-crystallographic 2-fold axis relating the two subunits. These results show trimethylamine dehydrogenase to be composed of two identical or very similar subunits each containing one [4Fe-4S]²⁺ center.     

救护白鹤与野生白鹤迁徙路线和活动规律差异分析

受伤和体弱白鹤的救护及放归是白鹤保护的重要方式之一。2014—2016年间,先后对8只救护白鹤和2只野生白鹤进行环志并安装卫星跟踪器,根据所获得的卫星跟踪数据来分析比较救护白鹤与野生白鹤在秋季迁徙路线和在重要中途停歇地的最大日活动距离、活动区分布和面积、生境类型等方面的异同。结果显示,救护白鹤放归当年与放归次年以及救护白鹤放归当年与野生白鹤的秋季迁徙路线和活动规律之间存在明显差异,但救护白鹤放归次年与野生白鹤之间差异不明显。(1)放归当年,4只救护白鹤在农田和水塘停歇1个月左右,停歇时长明显高于野生白鹤和放归次年的救护白鹤。(2)救护白鹤放归当年在跨海方式、登陆地点、停歇地点以及登陆后的迁徙方向上表现出多样性和不确定性,其中部分个体在迁徙过程中有停顿徘徊、迷失迁徙方向的现象,且跨越渤海和大别山的距离大于放归次年的救护白鹤和野生白鹤。(3)救护白鹤放归后4天内每日最大活动距离小,而后高低分化明显,无明显规律,而救护白鹤放归次年的每日最大活动距离规律变化与野生白鹤较一致。(4)与救护白鹤放归次年以及野生白鹤的活动规律相比,救护白鹤放归当年的栖息地位点变化频繁,具体表现为生境类型选择的多样化...     

Prevalence and resting behaviour of dengue vectors,Aedes aegypti and Aedes albopictus in dengue high risk urban settings in Colombo,Sri Lanka

Understanding local geographical variation in vector density and bionomics related to virus transmission are critical for planning effective vector control programs to control dengue virus transmission. This study investigated the prevalence and resting behaviour of Aedes aegypti and Ae. albopictus in three dengue high-risk areas in the Colombo District, Sri Lanka. Monthly sampling of resting adult mosquitoes was conducted from August 2019 to February 2020. Thirty-seven percent of the households (289/776) harboured Aedes mosquitoes, and 603 Aedes mosquitoes were collected. The proportion of Ae. aegypti was higher in the overall collection during the collection period (94% [569/603]), and 62% (352/569) were females. Significant monthly variations in Ae. aegypti were observed with respect to the indices: number of females per surveyed house (F/SH; p = 0.001), number of females per Aedes positive house (F/PH; p = 0.029), adult house index (AHI; p = 0.001), adult density (AD; p = 0.005) and resting ratio (RR; p = 0.001). AHI, AD, and RR had statistically significant positive correlations with monthly rainfall (p = 0.001, p = 0.011, and p = 0.002 respectively) and one-month lagged dengue cases (p = 0.002, p = 0.005, and p < 0.001 respectively). A statistically significantly higher proportion of Ae. aegypti females were caught resting indoors (N = 309, 88%) than outdoors (N = 43, 12%; p < 0.001). The most common resting areas were bedrooms (51%) & living/dining rooms (37%), and places were under or on furniture (47%) & hangings (34%) for Ae. aegypti. Conversely, 74% of female Ae. albopictus were collected outdoors. Results of this study could have strong implications to improve vector surveillance and control by early detection of dengue to detect outbreaks and minimization of disease transmission.     

Curiosity, Recruitment, and Chaos: A Tribute to Bill Ricker’s Inquiring Mind

Synopsis Through three versions of a handbook on computations for biological statistics of fish populations, W.E. “Bill” Ricker played a pivotal role in founding the field of quantitative fishery science. His interests, however, extended far beyond the confines of quantifiable events to a deep appreciation for the natural world. In this article, I trace his development of fishery models from the 1940s to the 1970s, using examples that illustrate his approach to statistics and biological systems analysis. I describe changes in technology and statistics that have made it possible to extend his research in new directions, although his approach still lies at the core of all modern fishery models. His gentle, inquiring spirit persisted long after his retirement in 1973, as I illustrate from personal experiences with him during the 1990s.     

Autoimmunity to glial antigens in vitro.

Lymph nodes cells and spleen cells in a 50:50 mixture from Fischer 344 rats were cultured on syngeneic glial cells and fibroblasts. In the glia cultures, but not in the fibroblast cultures, the lymphocytes were stimulated to a vivid blast transformation and mitotic activity with a peak after 7 days, after which they reverted to small- and medium-sized lymphocytes. The stimulated lymphoid cells were not cytotoxic to glial cells when tested in a microcytotoxicity assay. A fraction of the lymphoblasts and their progeny (approximately 4%) took a positive intracytoplasmic stain for γ-globulin immunoglobulin G after direct immunofluorescence. Efforts to demonstrate immunoglobulin produced and released into the culture medium by the stimulated cells were negative. The findings may indicate that among the lymphoid cells responding to the glial antigens under these conditions, there are suppressor cells that abrogate the killer cell effect.     

Comparison of Preoperative Alpha-blockade for Resection of Paraganglioma and Pheochromocytoma

ObjectivePhenoxybenzamine (nonselective, noncompetitive alpha-blocker) is the preferred drug for preoperative treatment of pheochromocytoma, but doxazosin (selective, competitive alpha-blocker) may be equally effective. We compared the efficacy of doxazosin vs phenoxybenzamine.MethodsWe conducted a prospective study of patients undergoing pheochromocytoma or paraganglioma resection by randomizing pretreatment with phenoxybenzamine or doxazosin at a single tertiary referral center. The high cost of phenoxybenzamine led to high crossover to doxazosin. Randomization was halted, and a consecutive historical cohort of phenoxybenzamine patients was included for a case-control study design. The efficacy of alpha-blockade was assessed with preinduction infusion of incremental doses of phenylephrine. The primary outcomes were mortality, cardiovascular complications, and intensive care unit admission. The secondary outcomes were hemodynamic instability index (proportion of operation outside of hemodynamic goals), adequacy of blockade by the phenylephrine titration test, and drug costs.ResultsTwenty-four patients were prospectively enrolled (doxazosin, n = 20; phenoxybenzamine, n = 4), and 15 historical patients treated with phenoxybenzamine were added (total phenoxybenzamine, n = 19). No major cardiovascular complications occurred in either group. The phenylephrine dose-response curves showed less blood pressure rise in the phenoxybenzamine than in the doxazosin group (linear regression coefficient = 0.008 vs 0.018, P = .01), suggesting better alpha-blockade in the phenoxybenzamine group. The median hemodynamic instability index was 14% vs 13% in the phenoxybenzamine and doxazosin groups, respectively (P = .56). The median highest daily cost of phenoxybenzamine was $442.20 compared to $5.06 for doxazosin.ConclusionPhenoxybenzamine may blunt intraoperative hypertension better than doxazosin, but this difference did not translate to fewer cardiovascular complications and is offset by a considerably increased cost.     

Structure of Fully Hydrated Fluid Phase Lipid Bilayers with Monounsaturated Chains

Quantitative structures are obtained at 30°C for the fully hydrated fluid phases of palmitoyloleoylphosphatidylcholine (POPC), with a double bond on the sn-2 hydrocarbon chain, and for dierucoylphosphatidylcholine (di22:1PC), with a double bond on each hydrocarbon chain. The form factors F(q _z ) for both lipids are obtained using a combination of three methods. (1) Volumetric measurements provide F(0). (2) X-ray scattering from extruded unilamellar vesicles provides ΙF(q _z )Ι for low q _z . (3) Diffuse X-ray scattering from oriented stacks of bilayers provides ΙF(q _z )Ι for high q _z . Also, data using method (2) are added to our recent data for dioleoylphosphatidylcholine (DOPC) using methods (1) and (3); the new DOPC data agree very well with the recent data and with (4) our older data obtained using a liquid crystallographic X-ray method. We used hybrid electron density models to obtain structural results from these form factors. The result for area per lipid (A) for DOPC 72.4 ± 0.5 Ų agrees well with our earlier publications, and we find A = 69.3 ± 0.5 Ų for di22:1PC and A = 68.3 ± 1.5 Ų for POPC. We obtain the values for five different average thicknesses: hydrophobic, steric, head-head, phosphate-phosphate and Luzzati. Comparison of the results for these three lipids and for our recent dimyristoylphosphatidylcholine (DMPC) determination provides quantitative measures of the effect of unsaturation on bilayer structure. Our results suggest that lipids with one monounsaturated chain have quantitative bilayer structures closer to lipids with two monounsaturated chains than to lipids with two completely saturated chains.