Are the birch trees in Southern England a source of <Emphasis Type="Italic">Betula</Emphasis> pollen for North London?

Birch pollen is highly allergenic. Knowledge of daily variations, atmospheric transport and source areas of birch pollen is important for exposure studies and for warnings to the public, especially for large cities such as London. Our results show that broad-leaved forests with high birch tree densities are located to the south and west of London. Bi-hourly Betula pollen concentrations for all the days included in the study, and for all available days with high birch pollen counts (daily average birch pollen counts >80 grains/m³), show that, on average, there is a peak between 1400 hours and 1600 hours. Back-trajectory analysis showed that, on days with high birch pollen counts (n = 60), 80% of air masses arriving at the time of peak diurnal birch pollen count approached North London from the south in a 180 degree arc from due east to due west. Detailed investigations of three Betula pollen episodes, with distinctly different diurnal patterns compared to the mean daily cycle, were used to illustrate how night-time maxima (2200–0400 hours) in Betula pollen counts could be the result of transport from distant sources or long transport times caused by slow moving air masses. We conclude that the Betula pollen recorded in North London could originate from sources found to the west and south of the city and not just trees within London itself. Possible sources outside the city include Continental Europe and the Betula trees within the broad-leaved forests of Southern England.     

Allergic symptoms caused by long-distance transported birch pollen

Birch pollen allergy is very common in northern Sweden, and the local flowering season never starts before the middle part of May. In the last week of April 1989 patients with birch pollen allergy developed typical symptoms requiring treatment. This pattern was confirmed in a group of patients who registered their symptoms in diaries, while contemporaneous pollen measurements demonstrated high amounts of birch pollen in the air. At that time in the northern part of Sweden, however, no birches were flowering. Meteorological data indicated that strong winds from the south-east during the period transported birch pollen from the Baltic states. Similar weather conditions in 1982, 1984 and in 1990 have also resulted in high amounts of birch pollen in the air long before the local flowering season. It is concluded that long distance transport of pollen may result in clinically significant allergy problems before, and even after the normal local season.     

The relationship between birch pollen,air pollution and weather types and their effect on antihistamine purchase in two Swedish cities

Exposure to elevated air pollution levels can aggravate pollen allergy symptoms. The aim of this study was to investigate the relationships between airborne birch (Betula) pollen, urban air pollutants NO₂, O₃ and PM₁₀ and their effects on antihistamine demand in Gothenburg and Malmö, Sweden, 2006–2012. Further, the influence of large-scale weather pattern on pollen-/pollution-related risk, using Lamb weather types (LWTs), was analysed. Daily LWTs were obtained by comparing the atmospheric pressure over a 16-point grid system over southern Sweden (scale ~3000 km). They include two non-directional types, cyclonic (C) and anticyclonic (A) and eight directional types depending on the wind direction (N, NE, E…). Birch pollen levels were exceptionally high under LWTs E and SE in both cities. Furthermore, LWTs with dry and moderately calm meteorological character (A, NE, E, SE) were associated with strongly elevated air pollution (NO₂ and PM₁₀) in Gothenburg. For most weather situations in both cities, simultaneously high birch pollen together with high air pollution had larger over-the-counter (OTC) sales of antihistamines than situations with high birch pollen alone. LWTs NE, E, SE and S had the highest OTC sales in both cities. In Gothenburg, the city with a higher load of both birch pollen and air pollution, the higher OTC sales were especially obvious and indicate an increased effect on allergic symptoms from air pollution. Furthermore, Gothenburg LWTs A, NE, E and SE were associated with high pollen and air pollution levels and thus classified as high-risk weather types. In Malmö, corresponding high-risk LWTs were NE, E, SE and S. Furthermore, occurrence of high pollen and air pollutants as well as OTC sales correlated strongly with vapour pressure deficit and temperature in Gothenburg (much less so in Malmö). This provides evidence that the combination of meteorological properties associated with LWTs can explain high levels of birch pollen and air pollution. Our study shows that LWTs represent a useful tool for integrated daily air quality forecasting/warning.     

软质与硬质地表对树木花粉日飘散变化的影响

以油松(Pinus tabulaeformis)、白玉兰(Magnolia denudata)、白皮松(Pinus bungeana)、臭椿(Ailanthus altissima)为被试树种,对比研究了春季静风晴朗天气中软质与硬质两种地表条件下不同树种在距树10m高度1.5m处花粉浓度的日变化特征。研究结果表明:(1)4个树种在相同地表环境的花粉浓度日变化趋势基本一致,但同一树种花粉浓度的日变化特征在软、硬两种地表条件下的差异明显。软质地面一天内空气中花粉浓度最大值出现14:00时前后,04:00时花粉浓度最低,这与全天内空气温度的变化正好一致,而与空气相对湿度的变化恰好相反。硬质地表近地空间空气中的花粉浓度则呈现"双峰型"日变化特征,两次峰值分别出现在14:00时和20:00时,硬质地面花粉浓度20:00时晚高峰的出现时间与硬质地面温度日峰值一致。(2)分析硬质地表20:00时花粉浓度高峰出现的原因可能与硬质地面的散热特性有关,硬质地面夜间释放积蓄热量的过程会在一定程度上增强近地面空气的对流运动,并辅助空气中的花粉粒子不断飘散,形成花粉浓度晚高峰。(3)相对于软质地面来讲,硬质地表对空气中花粉飘散的影响作用持续时间更长,这也在一定程度上延长了致敏花粉的危害时间,加剧了致敏花粉的污染程度。研究还进一步在花粉致敏树种栽植、地表覆盖方式等方面进行了讨论;同时建议花粉症患者根据花粉污染发生规律合理规避花粉浓度聚集高峰期出行,从而有效缓解致敏花粉对易感人群的健康威胁。     

Parameterization of the birch pollen diurnal cycle

The purpose of this study was to investigate the patterns of birch pollen counts over a diurnal cycle and propose a parameterization that is useful for inclusion into operational and research short- and long-term modeling for birch pollen atmospheric transport and deposition at different spatial scales. The evaluation of patterns of diurnal cycles on monthly and interannual bases has been done based on analysis of a 26-year time series of birch pollen counts from the Danish pollen measurement site in Copenhagen. The suggested parameterization, based on a simple trigonometric function, includes dependencies on the time of birch pollen maximum and minimum occurrence on a diurnal cycle, averaged concentration at the end of the previous day, and time shift.     

Miniaturized direct on air sampling filter quantification of pollen allergens

A recently in this journal reported luminescence immunoassay for the direct quantification of birch and grass pollen allergens on air sampling filters. DOSIS, has been miniaturized. By means of a commercially available chlorinated analogue of the previously used 1,2 dioxetane phosphate derivative as enzyme substrate, the air sampling filter diameter could be reduced from 25 mm to 13 mm. The procedure leads to a more than twenty times reduction of the previously reported limit of quantification for the grass pollen allergen.     

Cherry leaf roll virus in the female gametophyte and seed of birch and its relevance to vertical virus transmission

ELISA detected cherry leaf roll virus (CLRV) in infected birch leaf sap diluted 1/320 in buffer, in extracts of one infected leaf with nine healthy leaves and in leaf sap frozen for 2 wk. Similarly, ELISA detected CLRV in mixtures of one infected bud with four virus-free buds. Intensive bioassays and ELISA showed that in some trees CLRV was restricted to only a few branches whereas in others it occurred throughout the tree. The prevalence of CLRV in unmanaged birch populations in Britain was less (3%) than in Midlands street trees (17%). In CLRV-free birch trees that received pollen from infected ones, ELISA indicated that antigen was introduced into, and multiplied within, the embryos but not the seed coat or the pericarp/wings. In one instance, antigen was detected in a branch of an experimentally pollinated tree but not in those parts of the crown that had been exposed to open pollination. The proportion of seed germinating after crosses in which both parents were CLRV-free was greater than when either or both parents were infected but the largest difference occurred with infection in the female parent. Few embryos seemed to escape invasion with CLRV when the maternal tissue was naturally infected. Overall, seed transmission ranged between 0 and 38% (mean 17%) when only females in a cross were infected, and between 11 and 75% (mean 30%) when only the males were infected. Assuming no selective advantage that would help infected plants to achieve reproductive age, we found that CLRV would be lost from a birch population within two generations if transmitted only through seed. Embryos in seeds from CLRV-infected birch that received CLRV-free pollen differed from their healthy counterparts in being shrunken and suspended in a loosely fibrillar matrix that contained numerous virus-like particles in tubular inclusions. In two trees, CLRV-free pollen tended to fertilise a greater percentage of ovules than did CLRV-infected pollen. Seedlings derived from infected seed and cuttings from naturally-infected trees grew less rapidly than their healthy counterparts. In still air, most birch pollen liberated from a height of 3·5 m fell within 3 m of the drop zone and none was detected 10 m from the source. Field observations on the patterns of virus spread as measured by seedling infection were consistent; about 3% of seedlings from a tree 6·9 m away from the nearest source of inoculum were infected but no infected seedlings were detected in more distant trees, even though each was experimentally infectible with CLRV and pollen from the infected tree germinated on their stigmas.     

Quantitative DNA Analyses for Airborne Birch Pollen

Birch trees produce large amounts of highly allergenic pollen grains that are distributed by wind and impact human health by causing seasonal hay fever, pollen-related asthma, and other allergic diseases. Traditionally, pollen forecasts are based on conventional microscopic counting techniques that are labor-intensive and limited in the reliable identification of species. Molecular biological techniques provide an alternative approach that is less labor-intensive and enables identification of any species by its genetic fingerprint. A particularly promising method is quantitative Real-Time polymerase chain reaction (qPCR), which can be used to determine the number of DNA copies and thus pollen grains in air filter samples. During the birch pollination season in 2010 in Mainz, Germany, we collected air filter samples of fine (<3 μm) and coarse air particulate matter. These were analyzed by qPCR using two different primer pairs: one for a single-copy gene (BP8) and the other for a multi-copy gene (ITS). The BP8 gene was better suitable for reliable qPCR results, and the qPCR results obtained for coarse particulate matter were well correlated with the birch pollen forecasting results of the regional air quality model COSMO-ART. As expected due to the size of birch pollen grains (~23 μm), the concentration of DNA in fine particulate matter was lower than in the coarse particle fraction. For the ITS region the factor was 64, while for the single-copy gene BP8 only 51. The possible presence of so-called sub-pollen particles in the fine particle fraction is, however, interesting even in low concentrations. These particles are known to be highly allergenic, reach deep into airways and cause often severe health problems. In conclusion, the results of this exploratory study open up the possibility of predicting and quantifying the pollen concentration in the atmosphere more precisely in the future.     

Long distance pollen transport cause problems for determining the timing of birch pollen season in Fennoscandia by using phenological observations

The male flowering and leaf bud burst of birch take place almost simultaneously, suggesting that the observations of leaf bud burst could be used to determine the timing of birch pollen release. However, long‐distance transport of birch pollen before the onset of local flowering may complicate the utilization of phenological observations in pollen forecasting.

We compared the timing of leaf bud burst of silver birch with the timing of the stages of birch pollen season during an eight year period (1997–2004) at five sites in Finland. The stages of the birch pollen season were defined using four different thresholds: 1) the first date of the earliest three‐day period with airborne birch pollen counts exceeding 10 grains m^?3 air; and the dates when the accumulated pollen sum reaches 2) 5%; 3) 50% and 4) 95% of the annual total. Atmospheric modelling was used to determine the source areas for the observed long‐distance transported pollen, and the exploitability of phenological observations in pollen forecasting was evaluated.

Pair‐wise comparisons of means indicate that the timing of leaf bud burst fell closest to the date when the accumulated pollen sum reached 5% of the annual total, and did not differ significantly from it at any site (p<0.05; Student‐Newman‐Keuls test). It was found that the timing of leaf bud burst of silver birch overlaps with the first half of the main birch pollen season. However, phenological observations alone do not suffice to determine the timing of the main birch pollen season because of long‐distance transport of birch pollen.     

The start of the birch pollen season in Finnish Lapland: separating non‐local from local birch pollen and the implication for allergy sufferers

Determining the start of the birch pollen season requires the reliable separation of non‐local from locally produced birch pollen. The research was undertaken close to the latitudinal birch tree line at the Kevo Subarctic Research Institute (69°45′N 27°01′E) in northern Finland. By comparing phenological and aerobiological observations, the proportion of birch pollen present in the air before local anthesis commences can be delimited. We coupled this with data of pollen deposition monitored by means of a modified Tauber trap. The dominant birch species at Kevo is the mountain birch Betula pubescens ssp. czerepanovii, whereas B. pubescens ssp. pubescens is very rare, hence we consider the proportion of the southerly B. pubescens‐type pollen deposited in the pollen trap to be non‐local in origin.

We did not observe any trend towards an earlier start of the phenologically observed mountain birch anthesis at Kevo as predicted from work elsewhere. Moreover, the fixed 2.5% threshold method for determining the birch pollen season proved not to be applicable since in many years this threshold was reached before the end of continuous snow cover. The results indicate that in some years non‐local birch pollen contributes considerably to the allergen load in Lapland with up to 57% of the total birch pollen sum being recorded before the day on which local anthesis commenced, and up to 70% of the annual birch pollen deposited being of the southerly birch type.     

Exploring the spatio-temporal relationship between two key aeroallergens and meteorological variables in the United Kingdom

Constructing accurate predictive models for grass and birch pollen in the air, the two most important aeroallergens, for areas with variable climate conditions such as the United Kingdom, require better understanding of the relationships between pollen count in the air and meteorological variables. Variations in daily birch and grass pollen counts and their relationship with daily meteorological variables were investigated for nine pollen monitoring sites for the period 2000–2010 in the United Kingdom. An active pollen count sampling method was employed at each of the monitoring stations to sample pollen from the atmosphere. The mechanism of this method is based on the volumetric spore traps of Hirst design (Hirst in Ann Appl Biol 39(2):257–265, 1952). The pollen season (start date, finish date) for grass and birch were determined using a first derivative method. Meteorological variables such as daily rainfall; maximum, minimum and average temperatures; cumulative sum of Sunshine duration; wind speed; and relative humidity were related to the grass and birch pollen counts for the pre-peak, post peak and the entire pollen season. The meteorological variables were correlated with the pollen count data for the following temporal supports: same-day, 1-day prior, 1-day mean prior, 3-day mean prior, 7-day mean prior. The direction of influence (positive/negative) of meteorological variables on pollen count varied for birch and grass, and also varied when the pollen season was treated as a whole season, or was segmented into the pre-peak and post-peak seasons. Maximum temperature, sunshine duration and rainfall were the most important variables influencing the count of grass pollen in the atmosphere. Both maximum temperature (pre-peak) and sunshine produced a strong positive correlation, and rain produced a strong negative correlation with grass pollen count in the air. Similarly, average temperature, wind speed and rainfall were the most important variables influencing the count of birch pollen in the air. Both wind speed and rain produced a negative correlation with birch pollen count in the air and average temperature produced a positive correlation.     

Testing the age and viability of airborne pollen

To study the aerobiological processes directly, it is important to differentiate between fresh and older pollen grains. Different methods were tested for this purpose using birch (Betula) pollen. Simple general stains stained also dead grains. More specific histochemical techniques (nitro blue tetrazolium and isatin) stained a high percentage of the grains even after eight days, although most of the germination ability was lost already in 2–3 days. Of the methods tried, the in vitro germination test was thus the most sensitive in differentiating between fresh and older pollen grains. To test the germination ability of airborne pollen it was collected by a suction pump on filters. Sectors of filters were incubated on a thin layer of agar on objective glasses in moist Petri dishes in +30°C for 24 hours. The germination ability was presumed to vary during the pollen season, but this was not found in this preliminary study. The diurnal variation in germination ability was clear. During or near diurnal peak concentrations the percentage of germination ability significantly higher than during diurnal minima and during intermediate concentrations.     

A comparative study of airborne pollen concentrations of three allergenic types

Airborne concentrations of pollen from Betula (birch), Poaceae (grasses) and Artemisia (mugwort) are compared during a seven year period (90–96) with respect to both quantitative and seasonal aspects, at three different sampling sites, one in Estonia (Tartu) and two in Sweden (Stockholm and Roma on the island of Gotland). All three taxa occur in the region and are well‐known causes of allergic sensitisation. The annual total and peak values of birch, grass and mugwort pollen were found to be much higher in Tartu than in Stockholm and Roma. Both the birch and the grass pollen seasons ended later in Stockholm than in Roma and Tartu. The mugwort flowering season always began earlier in Stockholm than at the other sites, and more days elapsed between start day and peak day in Stockholm than in Tartu.     

Climate change effect on Betula (birch) and Quercus (oak) pollen seasons in the United States

Climatic change is expected to affect the spatiotemporal patterns of airborne allergenic pollen, which has been found to act synergistically with common air pollutants, such as ozone, to cause allergic airway disease (AAD). Observed airborne pollen data from six stations from 1994 to 2011 at Fargo (North Dakota), College Station (Texas), Omaha (Nebraska), Pleasanton (California), Cherry Hill and Newark (New Jersey) in the US were studied to examine climate change effects on trends of annual mean and peak value of daily concentrations, annual production, season start, and season length of Betula (birch) and Quercus (oak) pollen. The growing degree hour (GDH) model was used to establish a relationship between start/end dates and differential temperature sums using observed hourly temperatures from surrounding meteorology stations. Optimum GDH models were then combined with meteorological information from the Weather Research and Forecasting (WRF) model, and land use land coverage data from the Biogenic Emissions Land use Database, version 3.1 (BELD3.1), to simulate start dates and season lengths of birch and oak pollen for both past and future years across the contiguous US (CONUS). For most of the studied stations, comparison of mean pollen indices between the periods of 1994–2000 and 2001–2011 showed that birch and oak trees were observed to flower 1–2 weeks earlier; annual mean and peak value of daily pollen concentrations tended to increase by 13.6 %–248 %. The observed pollen season lengths varied for birch and for oak across the different monitoring stations. Optimum initial date, base temperature, and threshold GDH for start date was found to be 1 March, 8 °C, and 1,879 h, respectively, for birch; 1 March, 5 °C, and 4,760 h, respectively, for oak. Simulation results indicated that responses of birch and oak pollen seasons to climate change are expected to vary for different regions.     

Diurnal gait fluctuations in single- and dual- task conditions

ABSTRACT

Gait is one of the most basic movements, and walking activity accomplished in dual task conditions realistically represents daily life mobility. Much is known about diurnal variations of gait components such as muscle power, postural control, and attention. However, paradoxically only little is known about gait itself. The aim of this study was to analyze whether gait parameters show time-of-day fluctuation in simple and dual task conditions. Sixteen young subjects performed sessions at five specific hours (06:00, 10:00, 14:00, 18:00 and 22:00 h), performing a single (walking or counting) and a dual (walking and counting) task. When performing gait in dual task conditions, an additional cognitive task had to be carried out. More precisely, the participants had to count backwards from a two-digit random number by increments of three while walking. Spatio-temporal gait parameters and counting performance data were recorded for analysis. Walking speed significantly decreased, while stride length variability increased when the task condition switched from single to dual. In the single-task condition, diurnal variations were observed in both walking speed and counting speed. Walking speed was higher in the afternoon and in the evening (14:00 and 22:00 h) and lower in the morning (10:00 h). Counting speed was maximum at 10:00 and 14:00 h and minimum at 18:00 h. Nevertheless, no significant diurnal fluctuation was substanytiated in the dual task condition. These results confirm the existing literature about changes in gait between single and dual task conditions. A diurnal pattern of single-task gait could also be highlighted. Moreover, this study suggests that diurnal variations faded in complex dual task gait, when the cognitive load nearly reached its maximum. These findings might be used to reduce the risk for falls, especially of the elderly.     

Air and surface soil samples – two different pairs of shoes? Comparing the pollen spectrum on different days of the pollen season

The pollen spectra of air and surface soil samples from a rooftop (at 14 m) and from ground level (at 1.6 m) in the suburbs of Vienna (Austria) were compared. Two soil samples and two air samples were taken on four different days to account for possible differences: in winter when no pollination occurred (reference day), in spring during the main flowering of Betula (birch day), in spring/summer during the main flowering of Poaceae (grass day), and in autumn during the main flowering of Ambrosia (ragweed day). Thirty-five different pollen types were used to describe the pollen spectra. Frequencies of certain pollen types reflect a seasonal impact on both the surface soil and air samples and show a similarity between air and soil samples on most of the days. However, the seasonal impact is higher in the air samples and shows a high consistency for ground and rooftop level. Kendall’s tau correlation coefficients further substantiate the similarities of the samples especially for the pollen season days. Exceptions include the winter day when pollination was low and the air samples recorded nearly no pollen at all, and the ragweed day when Ambrosia pollen was abundant in three of four samples but not in the ground surface soil sample. Thus, (1) air and surface pollen samples record similar signals during the pollen season but not during the ragweed and winter season and (2) air and surface pollen samples show the impact of local vegetation also in pollen traps located at different heights.     

Birch pollen production,transport and deposition for the period 1984–1993 at Kevo,northernmost Finland

Summary Betula pollen production and flowering, pollen transport and pollen deposition are considered for the mountain birch region of northern Finland for the ten-year period 1984–1993. The most abundant flowering year was 1989 and, after that, 1985. In these years the highest values were also recorded for pollen in the air. There is a significant correlation between the amount of pollen released and the thermal sum of the previous year. In terms of pollen deposition the peak years were 1989 and 1986. The correlation between the amount of pollen in the air and that being deposited on the ground is also statisticaly significant. It is evident that some birch pollen is already present in the air before local flowering begins and that, in some years, this non-local pollen can account for more than 20% of the yearly total. This preflowering proportion was highest in 1985 and 1993, the latter being a prolific flowering year in the south of the country. There is a clear relationship between the proportion of the non-local pollen in the air and the proportion ofBetula pubescens/pendula type pollen deposited on the ground and, conversely, there is a significant correlation between the amount of local pollen in the air and the amount ofBetula tortuosa plusB. nana type pollen being deposited on the ground. The questions both of the viability of this long-distance pollen and of its ability to cause allergic reactions are considered. An assessment is also made of the degree to which fossil birch pollen assemblages can be realistically interpreted in terms of local vegetation if a varying proportion of the same pollen type is non-local.     

转基因白桦的花粉活力及外源基因的遗传表达分析

采用荧光素二乙酸酯（FDA）染色比较分析转基因白桦花粉的活力的结果表明,转基因白桦的花粉活力均低于非转基因白桦。应用多重PCR和Northern杂交技术分析表明,转基因白桦花粉中有外源基因整合和转录表达。检测转基因白桦花粉中gus报告基因的活性,显示gus报告基因在花粉表达。     

Airborne birch pollen in Neuchâtel (Switzerland): onset, peak and daily patterns

An accurate forecast of the starting point of thebirch pollen season in Neuchâtel can be made byadding the positive daily average air temperature fromFebruary 1st onward until the figure 270 is reached.At this point, the birch trees are ready to bloom.After that, the daily average temperature has toexceed 10 °C to allow pollen release.Today, the birch pollen season starts some 19 daysearlier in the year than in the 1980's, a consequenceof a recent climate change.The daily patterns of airborne birch pollen isirregular. Moreover, pollen concentrations frequentlyexceed the threshold of the appearance of allergicsymptoms, except during rainfall. Therefore, the onlybehavioral recommendation that can be given to peopleallergic to birch pollen is to shorten as much aspossible the contact with outdoor air during the mainbirch pollen season.     

Life tables of Neoseiulus cucumeris exclusively fed with seven different pollens

The juvenile development and survival, and demographic parameters of the predatory mite Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) fed on pollen of castor bean, tulip, apple, Christmas cactus, horse-chestnut, maize, and birch were assessed under laboratory conditions. Deprivation of food and pollen of castor bean plants resulted in 100 % juvenile mite mortality. Feeding mites with tulip and horse-chestnut pollen resulted in the shortest development and the highest total fecundity. Adult mites fed on birch, tulip, maize, and apple pollen lived significantly longer compared with those fed on pollen of horse-chestnut and Christmas cactus. The intrinsic rate of natural increase ranged between 0.1013 ♀♀/♀/day for maize and 0.1806 ♀♀/♀/day for horse-chestnut pollen as food. Net reproductive rate was the lowest when fed with maize pollen and highest when fed with horse-chestnut pollen. Population doubling time was highest on maize pollen and shortest on horse-chestnut pollen. Our study revealed that birch, tulip, horse-chestnut, apple, and maize pollen can be used by N. cucumeris from early spring to late summer as a suitable alternative food in periods when prey in the field are scarce or absent.