A method for the estimation of gene flow parameters from a population structure caused by restricted gene flow and genetic drift

Summary A method has been developed which enables the estimation of the plant gene flow parameters _p (pollen dispersal), _s (seed dispersal) and t (outcrossing rate) from a selection-free continuously structured population in equilibrium. The method uses Wright's F-coefficients and introduces a new F-function which describes the genetic similarity as a function of the spatial distance. The method has been elaborated for wind pollinated plant species but can be modified for insect pollination and for animal species. In practice allozymes will provide for the necessary neutral genetic variation. The more loci used and the more intermediate the gene frequencies, the more reliable the results. For the estimation of _p and t together (when the outcrossing rate is not known) at least two chromosomally unlinked loci are required. The method for estimating _s depends on whether the plant species is annual or perennial. The mechanism of selfing has been analysed by the explanation of the value of t by three components: population density (d), pollen flow (_p) and relative fertilization potential of own pollen (Z). The concepts of neighbourhood size and isolation by distance, developed by Wright, who used a single gene flow parameter , have been extended to the situation which is realistic for seed plants, using all three parameters _p, _s and t. When _p is large with respect to _s, _s largely determines the value of the neighbourhood size, whereas _p is the most dominating factor in isolation by distance. The use of local effective population size and mean gene transport per generation instead of neighbourhood size and neighbourhood area, respectively, is proposed to avoid confusion. Computer simulations have been carried out to check the validity and the reliability of the method. Populations of 200 plants, using two or three loci with intermediate allele frequencies, gave good results in the calculation of _p with known value of t and of _s and N_e. With unknown t, especially with lower values of t, larger populations of at least 1,000 plants are necessary to obtain reasonably accurate results for _p and mean gene transport per generation M.Grassland Species Research Group Publication No. 81     

Effect of rainstorms on heterotrophic bacterial activity in a hypertrophic African lake

Hartbeespoort Dam is a hypertrophic man-made lake which is located in the Transvaal Province of South Africa. This region has recently experienced its most severe drought of the century. However, on three occasions in the summer rainy seasons of 1984 and 1985, major rainfalls (> 50 mm) occurred which caused large inflows to the lake. Inflowing river water entered as a density current causing marked silting of the water. Within the epilimnion (0–10 m) prior to these rainfalls there was usually no variation of bacterial numbers with depth, but heterotrophic bacterial activity (glucose uptake) decreased with depth concomitant with primary production. With the increased river inflow bacterial numbers did not increase but bacterial activity at the bottom of the epilimnion (10 m) increased to as high as 2.7 µg C l^–1 h^–1 in January 1985, reversing the depth profile of bacterial activity within the epilimnion. This resulted in decreased glucose concentrations (K_t + S_n) and turnover times. Heterotrophic activity per cell increased by between 2.5 and 5 times. These data demonstrate that storm events are important phenomena causing short-term changes in the metabolic activity of planktonic heterotrophic bacteria in lakes.     

A new technique for monitoring pollen flow in orchids

Summary The orchid Prasophyllum fimbria is pollinated by nectar-feeding native bees and wasps. The pollinia are patially separated from the viscidium by a stipe so that pollinia can be labelled with coloured histochemical stains without interfering with pollinarium removal. Pollen flow was monitored by following the movement of the coloured pollen in several populations of P. fimbria in Western Australia. Statistical analysis confirmed that pollen labelling did not interfere with pollinarium removal or subsequent pollination of the labelled flower. Fifty eight labelled pollinaria were removed by vectors from 16 test spikes, with a total of 125 flowers on 47 spikes receiving labelled pollen. An average of 2 flowers received pollen for every pollinium removed but up to 6 flowers received pollen from a single collinium. No significant differences between mean vector flights and pollen flow distances were detected. On average, geitonogamous transfers only accounted for 22% of all pollinations. This is a simple and inexpensive technique for the direct labelling of pollen with minimal disruption to the pollination system and may have applications in other plant families.     

Endocytosis of α1-acid glycoprotein variants and of neoglycoproteins containing mannose derivatives by a mouse hybridoma cell line (2C11–12). Comparison with mouse peritoneal macrophages

Macrophages from various origins are known to express membrane lectins that mediate the endocytosis of mannose-bearing glycoconjugates. Most macrophage tumor cell-lines lack such receptors. In this paper we show by flow cytometry analysis that a newly generated macrophage hybridoma (2C_11–12), which displays several macrophage characteristics, also expresses mannose membrane lectins, resulting in the internalization of fluoresceinylated neoglycoproteins into acidic compartments.Thioglycolate elicited mouse peritoneal macrophages and the 2C_11–12 hybridomas were compared by flow cytometry with regard to the binding and endocytosis of ₁-acid glycoprotein (AGP) variants separated by affinity chromatography on immobilized concanavalin A. AGP C eluted specifically with methyl -mannopyranoside, which contains two bi-antennary oligosaccharides, was endocytosed as mannosylated serum albumin (Man-BSA). In both types of macrophages, the fluoresceinylated ligands were internalized in acidic compartments as demonstrated by the fluorescence intensity increase upon monensin post-incubation. However the behaviour of the internalized ligands was found to be quite different. AGP C and Man-BSA were rapidly degraded by thioglycolate elicited peritoneal macrophages and excreted in the medium as small peptide fragments; conversely they remained a longer time in the 2C_11–12 hybridoma.     

Biological activities caused by far-infrared radiation

Contrary to previous presumption, accumulated evidence indicates that far-infrared rays are biologically active. A small ceramic disk that emist far-infrared rays (4–16 m) has commonly been applied to a local spot or a whole part of the body for exposure. Pioneering attempts to experimentally analyze an effect of acute and chronic radiation of far-infrared rays on living organisms have detected a growth-promoting effect in growing rats, a sleep-modulatory effect in freely behaving rats and an insomiac patient, and a blood circulation-enhancing effect in human skin. Question-paires to 542 users of far-infrared radiator disks embedded in bedelothes revealed that the majority of the users subjectively evaluated an improvement of their health. These effects on living organisms appear to be non-specifically triggered by an exposure to far-infrared rays, which eventually induce an increase in temperature of the body tissues or, more basically, an elevated motility of body fluids due to decrease in size of water clusters.     

Ischemic flow threshold for striatal dopamine release in rats

To determine the level of cerebral blood flow reduction which causes striatal dopamine release, extracellular dopamine and cerebral blood flow was simultaneously determined using in vivo brain dialysis and a hydrogen clearance method, respectively, in the striatum of spontaneously hypertensive rats, before and during experimental cerebral ischemia. The ischemic flow threshold for neurotransmitter dopamine release was found to be 20% of the resting value or 8–10 ml/100g/min of cerebral blood flow, being similar to those for energy and membrane failures.     

心房钠尿因子对麻醉家兔局部血流的影响

在42只麻醉家兔,观察了静脉注射心房肽Ⅱ(AtriopeptinⅡ,APⅡ)对局部血流量以及动脉内注射 AP Ⅱ 对局部血管阻力的影响。结果如下:(1)静脉注射 APⅡ(30μg/kg)5min后,平均动脉压(MAP)降低11.0±1.5mmHg(n=8,M±SE,下同),与溶剂对照组相比有明显差异(P相似文献   

肾神经在扩张心房时对尿量和尿钠排出的作用

单侧肾去神经的麻醉狗,用乳胶小囊扩张肺静脉-心房连接部,观察到神经完好肾的尿流量与排钠量均显著增加(P<0.01);去神经肾的尿流量仍显著增加(P<0 01),但排钠量无明显变化(P>0.05);两侧肾的肾小球滤过率(GFR)及肾血浆流量(RPF)均保持稳定;神经完好肾的静脉血浆肾素活性(PRA)及血管紧张素Ⅱ水平(PAⅡ)均明显降低,PAⅡ降低的幅度与尿流量增加的幅度无相关(r=-0.2975,P>0.05);与排钠量增加的幅度也无相关(r=-0.2359,P>0.05);去神经肾的PRA和PAⅡ都没有显著变化。说明在刺激心房感受器引起的利尿与尿钠排泄的反应中,肾神经主要促进肾对尿钠的排出。肾神经的这种作用既不是通过改变GFR和RPF,也不是抑制肾素的释放,而可能是由于直接影响肾小管对钠的重吸收。     

Brain Metabolism and Intracellular pH During Ischaemia: Effects of Systemic Glucose and Bicarbonate Administration Studied by 31P and 1H Nuclear Magnetic Resonance Spectroscopy In Vivo in the Lamb

Brain metabolism and intracellular pH were studied during and after episodes of incomplete cerebral ischaemia in lambs under sodium pentobarbitone anaesthesia. 31P and 1H magnetic resonance spectroscopy was used to monitor brain pHi and brain concentrations of inorganic phosphate (Pi), phosphocreatine (PCr), beta-nucleoside triphosphate (beta NTP), and lactate. Simultaneous measurements were made of arterio-cerebral venous concentration differences (AVDs) for oxygen, glucose, and lactate. Cerebral ischaemia was induced by a combination of bilateral carotid clamping and hypotension, and the acute effects of systemic administration of glucose and sodium bicarbonate were examined. The molar ratio of glucose to oxygen uptake by the brain (6G/O2) increased above unity during cerebral ischaemia. Statistically significant AVDs for lactate were not observed. Cerebral ischaemia was associated with a reduction in brain pHi PCr/Pi ratio, and an increase in brain lactate. No effect of arterial plasma glucose on brain lactate concentration or brain pHi was evident during cerebral ischaemia or in the postischaemic period. Administration of sodium bicarbonate systemically in the postischaemic period was associated with a rise in arterial and brain tissue PCO2. A fall in brain pHi occurred which was attributable in part to coincidental brain lactate accumulation. The increase in brain lactate measured by 1H nuclear magnetic resonance in vivo during ischaemia was insufficient to account for the change in buffer base calculated to have occurred from previous estimates of brain buffering capacity.