Spatial variation of pollen deposition in north london

Pollen data from a monitoring network of 14 impact samplers in Islington, North London are used to investigate spatial variations in the abundance of Gramineae, Betula and Platanus pollen deposition. Weekly accumulative pollen counts were collected from January through to October over two consecutive years. Differences in deposition between sites are examined in relation to topography, local sources, and climatic variables.     

Vertical variation in urticaceae airborne pollen concentration

The pollen contents at different heights (1.5 and 15 m) of species of the Urticaceae family have been studied by sampling with Hirst type volumetric samplers. In order to achieve this, the two pollen types belonging to this family have been treated separately,Urtica urens-Parietaria sp. on the one hand andUrtica membranacea on the other, the latter having a smaller pollen grain. The results show that meteorological factors are bound to influence the behaviour of both these types of pollen in relation to height. With damp weather the pollen contents vary very slightly at different heights while when the weather is dry and calm, differences in pollen content at different heights become more significant. Nevertheless, when the atmosphere is stratified, the behaviour of each pollen type is different. The results show that, for most of the months considered, there is a higher pollen content ofU. membranacea at upper heights, whileU. urens-Parietaria sp. has higher levels of pollen content at a lower height. High temperatures, absence of rain and calm weather conditions favour the presence of convective phenomena which in turn create a favourable atmosphere for the vertical transportation of the small pollen grains ofU. membranacea, which are better represented in the samplers placed at 15 m.     

Diurnal variation of chosen airborne pollen at five sites in Poland

The aerobiological investigations were carriedout at five sites located in different climaticand geobotanical regions in Poland. The diurnalperiodicity of Alnus, Betula, Secale,Poaceae, Urtica, and Artemisia wasstudied during two successive years. The taxawere chosen on the basis of pollen grainabundance and allergenity. The pollen wascollected with a Burkard spore trap. Twelvetransversal transverses of microscope slidescorresponding to two-hour periods wereanalysed. The diurnal variations ofPoaceae, Alnus and Betula were irregularand varied between sites and years; highconcentrations were observed at different hoursof the day and night. Diurnal concentrations of Secale, Urtica and Artemisia hadonly one maximum in the middle of the day,constant between sites and years. The lowestconcentrations were observed between eveningand early morning. There was no close relationbetween the time of the liberation ofAlnus, Betula and Poaceae pollen and thetime of the maximum pollen counts. There was aseveral hour delay observed between the timeof Secale pollen liberation and maximumconcentration of airborne pollen.     

Diurnal variation in airborne pollen concentrations of the selected taxa in Zagreb, Croatia

The number of individuals allergic to plant pollen has recently been on a constant increase. The knowledge of diurnal distribution and abundance of allergenic pollen types, their patterns and response to source position and weather is useful to correlate hay fever symptoms with the presence of allergenic pollen in the atmosphere. The aim of this study was to determine diurnal distribution of total airborne pollen, pollen of particular allergenic taxa, possible variation in diurnal pollen distribution at measuring sites placed at different heights, and effect of some meteorological parameters on airborne pollen concentrations. A 7-day Hirst-type volumetric pollen trap was used for pollen sampling. Qualitative and quantitative pollen analysis was performed under a light microscope (magnification x400). Total pollen of all plant taxa (Ambrosia sp., Betula sp., Cupressaceae, Urticaceae, Poaceae, Quercus sp., Fraxinus sp., Alnus sp., Corylus sp., Populus sp., Pinus sp., Picea sp.) observed showed a regular diurnal distribution at both sampling sites in both study years, with a rise in the pollen concentration recorded after 4.00 a.m. and 6.00 a.m., respectively. The peak pollen concentration occurred between 12.00 a.m. and 4.00 p.m., and the lowest diurnal pollen concentrations were recorded overnight. About 50% of the 24-h pollen concentration were released to the atmosphere between 10.00 a.m. and 4.00 p.m. The timing and size of diurnal peaks were closely related to high temperature, low humidity and south-west maximum wind direction.     

Diurnal variation and reliability of the urine lactate concentration after maximal exercise

The postexercise urine lactate concentration is a novel valid exercise biomarker, which has exhibited satisfactory reliability in the morning hours under controlled water intake. The aim of the present study was to investigate the diurnal variation of the postexercise urine lactate concentration and its reliability in the afternoon hours. Thirty-two healthy children (11 boys and 21 girls) and 23 adults (13 men and 10 women) participated in the study. All participants performed two identical sessions of eight 25 m bouts of maximal freestyle swimming executed every 2 min with passive recovery in between. These sessions were performed in the morning and afternoon and were separated by 3–4 days. Adults performed an additional afternoon session that was also separated by 3–4 days. All swimmers drank 500 mL of water before and another 500 mL after each test. Capillary blood and urine samples were collected before and after each test for lactate determination. Urine creatinine, urine density and body water content were also measured. The intraclass correlation coefficient was used as a reliability index between the morning and afternoon tests, as well as between the afternoon test and retest. Swimming performance and body water content exhibited excellent reliability in both children and adults. The postexercise blood lactate concentration did not show diurnal variation, showing a good reliability between the morning and afternoon tests, as well as high reliability between the afternoon test and retest. The postexercise urine density and lactate concentration were affected by time of day. However, when lactate was normalized to creatinine, it exhibited excellent reliability in children and good-to-high reliability in adults. The postexercise urine lactate concentration showed high reliability between the afternoon test and retest, independent of creatinine normalization. The postexercise blood and urine lactate concentrations were significantly correlated in all cases, attesting to the validity of urine lactate as an index of anaerobic metabolism. We conclude that urine lactate, after normalization to creatinine, could be used in training practice either in the morning or in the afternoon. Further research is needed to assess the applicability of this novel exercise biomarker.     

Diurnal variation in the functioning of cowpea nodules

Nitrogenase (EC 1.7.99.2) activity of nodules of cowpea (Vigna unguiculata [L.] Walp), maintained under conditions of a 12-hour day at 30°C and 800 to 1,000 microeinsteins per square meter per second (photosynthetically active radiation) and a 12-hour night at 20°C, showed a marked diurnal variation with the total electron flux through the enzyme at night being 60% of that in the photoperiod. This diurnal pattern was, however, due to changes in hydrogen evolution. The rate of nitrogen fixation, measured by short-term ¹⁵N₂ assimilation or estimated from the difference in hydrogen evolution in air or Ar:O₂ (80:20; v/v), showed no diurnal variation. Carbon dioxide released from nodules showed a diurnal variation synchronized with that of nitrogenase functioning and, as a consequence, the apparent `respiratory cost' of nitrogen fixation in the photoperiod was almost double that at night (9.74 ± 0.38 versus 5.70 ± 0.90 moles CO₂ evolved per mole N₂ fixed). Separate carbon and nitrogen balances constructed for nodules during the photoperiod and dark period showed that, at night, nodule functioning required up to 40% less carbohydrate to achieve the same level of nitrogen fixation as during the photoperiod (2.4 versus 1.4 moles hexose per mole N₂ fixed).

Stored reserves of nonstructural carbohydrate of the nodule only partly satisfied the requirement for carbon at night, and fixation was dependent on continued import of translocated assimilates at all times. Measurements of the soluble nitrogen pools of the nodule together with ¹⁵N studies indicated that, both during the day and night, nitrogenous products of fixation were effectively translocated to all organs of the host plant despite low rates of transpiration at night. Reduced fluxes of water through the plant at night were apparently counteracted by increased concentration of nitrogen, especially as ureides, in the xylem stream.

     

Diurnal variation in the feeding pattern of rabbits

Laboratory rabbits maintained under controlled lighting and fed $\text{ad libitum}$ exhibit a weak but consistent diurnal fluctuation in feed intake. There are two major periods of eating; at the beginning and the end of the light period. This results in similar feed consumption for the light and dark periods. Water intake shows a similar diurnal variation to that of feed intake. If the normal lighting cycle is retarded by 6 hours, the animals adjust their diurnal rhythm of feeding behaviour to the new lighting cycle within 8 to 15 days. Comparative studies on rats are included.     

Diurnal fluctuation in saliva aldosterone concentration

We have measured saliva aldosterone concentration (SA) at frequent intervals in subjects going about their normal daytime activities. Four hourly sampling sufficed to give a reasonable estimate of mean diurnal SA but hourly sampling is necessary if it is desired to study the temporal pattern of SA. In subjects with normal or elevated mean levels, SA fluctuated considerably suggestive of several distinct episodes of aldosterone secretion. Such fluctuations show little correlation with the concentrations in saliva of glucocorticoids (cortisol + cortisone) nor are they consistent with a circadian rhythm of aldosterone secretion. We suggest that they may represent responses to such stimuli as eating, drinking or physical activity, and possibly to other as yet unidentified factors. These observations show the importance of comprehensive diurnal assessment of aldosterone level in physiological and pathological investigations. Because of its non-invasive nature and the high productivity of the assay, measurement of SA is ideally suited for this purpose.     

Diurnal variation of phytoplankton in Loch Lomond

A study of diurnal variation over a 48 hour period was undertaken in July 1973 to ascertain the extent and timing of some major chemical, physical and biological variables in Loch Lomond. The phytoplankton population was dominated by the diatom Tabellaria fenestrata, with a maximum abundance between 04.00 and 06.00 h in surface waters on both days. A distinct diurnal variation in cell numbers was also recorded. Chlorophyll a values also showed a regular pattern of variation with a single peak between 10.00 and 14.00 h each day. Some chemical changes appeared to be a direct consequence of phytoplankton multiplication. Nitrate-nitrogen showed a decrease in concentration coinciding with the period of cell multiplication, whereas dissolved silica concentrations only fell on the completion of this process. Other common diatoms displayed less distinct patterns of variation although Fragilaria crotonensis attained its maximum abundance in surface waters. Considerable variation was recorded in the number of organisms and chlorophyll a levels at 25 cm intervals in the upper metre of the water column, with large variations in standing-crop and chemical parameters in the space of one hour. Diurnal oscillations in the position of the thermocline were recorded, with the thermal discontinuity being at its greatest depth in the early hours of the morning. The hypolimnion and thermocline regions clearly acted as a source of nutrient supply to the epilimnion. From this investigation it is apparent that for the proper understanding of diurnal variation a 24 hour study alone is insufficient and may give rise to misleading results.Department of Botany, University of GlasgowDepartment of Botany, University of Glasgow     

Diurnal and seasonal variation of the equilibrium state between short-lived radon decay products and radon gas in ground-level air

To study seasonal and diurnal variations and the effect of meteorological parameters, the equilibrium factor F (i.e. the ratio of equilibrium equivalent radon daughter concentration and radon gas concentration) was determined as a result of measurements on a test field at Munich-Neuherberg, Germany, continuously from October 1995 through March 1997. On average, F was found to be 0.62±0.09 (95% confidence level). The time series of F showed no distinct seasonal variations. Nevertheless, typical diurnal variations as well as seasonal variations of the diurnal behaviour were observed. Generally, F was found to be increased in the early afternoon, i.e. under conditions of enhanced vertical mixing in the atmosphere. The daily differences between high and low values of F depended on the season. On average, low F values were characteristic for days with precipitation and high wind speed, i.e. under turbulent atmospheric conditions. Therefore, taking daily mean values into account, F was found to be positively correlated with the aerosol concentration, although a relationship between the diurnal behaviour of the aerosol concentration and that of F was not detectable. Received: 6 September 2000 / Accepted: 20 February 2001     

Diurnal variation of metabolites in three individual participants

The circadian system influences virtually all biological functions. Understanding the impact of circadian variation on metabolism may provide insight into mechanisms of circadian-associated disorders and guide the implementation of chrono-therapy. Previous research has reported circadian variation in 7–20% of metabolites in human blood. In this study, untargeted metabolomics profiles were measured using blood of two healthy men and one healthy woman, collected every 2 h for up to 48 h under carefully controlled conditions. The pattern of variation of each metabolite over time was examined on each participant separately, using both one- and two-order harmonic models. A total of 100 of 663 metabolites, representing all metabolite categories, showed diurnal rhythmic concentrations that exceeded the Bonferroni threshold (P < 2.5 × 10^?5). Overall, peak times of many metabolites were clustered during the afternoon-midnight, including the majority of amino acids, all peptides, all lysolipids and all phospholipids, whereas the majority of steroids peaked in the morning. We observed substantial inter-individual variation for both peak times and amplitudes in these three subjects. In conclusion, at least 15% of blood metabolites, representing a broad group of biological pathways, exhibit diurnal variation in three participants. The average peak times of most of these metabolites are clustered in morning or afternoon-midnight. Further work is needed to validate and extend this work in more individuals.     

Ambrosia pollen in the air of Lublin, Poland

Studies on Ambrosia pollen concentrations were carried out in Lublin in the period 1995–2004. The effects of a number of meteorological factors were analysed. In the first period of the study, the gravimetric method was used (1995–1999), while in the second period, the volumetric method was applied. The results show an increasing trend in the amount of airborne pollen. The Ambrosia pollen season in Lublin lasts from August to October. Over a period of 5 years, the highest number of pollen grains was recorded in September (53%), followed by August (44%) and October (3%). There were wide variations in annual totals. The annual total pollen counts was 167–1180 grains, with the peak value in 2002. Maximum daily pollen concentrations (56–312 pollen grains m⁻³) were recorded in the first half of August and in the first half of September. On the days when high Ambrosia pollen concentrations occurred, the temperature was above 21°C and the winds were mainly from the southeast, south and east. Maximum intradiurnal concentrations of pollen grains occurred in the afternoon hours. These results indicate, to some degree, that Ambrosia pollen is transported for long distances before descent.     

Diurnal variation of dopamine content in the rat pineal gland

Levels of norepinephrine and dopamine in the rat pineal gland were determined by a radioenzymatic assay with modifications to separate the reaction products. Catecholamines were converted to 3-O-methylated derivatives in the presence of catechol-O-methyltransferase (EC 2.1.1.1) and S-adenosyl-L-[methyl-³H]-methionine. Following solvent extraction of the labelled normetanephrine and 3-methoxytyramine, the amines were separated by high-performance liquid chromatography. Contents of both catecholamines in the pineal gland varied with a 24-hr rhythm. The content of norepinephrine was maximal at about 6 A.M. (lights on from 8 A.M. to 8 P.M.) and declined gradually thereafter. In contrast to the level of norepinephrine, the dopamine level was highest at about 0 A.M. and fell rapidly to reach a trough after the lights were turned on. These observations suggest that the diurnal variation of norepinephrine is generated by changes in the contents of dopamine in sympathetic nerve terminals innervating the pineal.