Seasonal variation in gastric myoelectrical activity in young Japanese females

In order to test our hypothesis that there is seasonal variation in digestion and absorption of dietary carbohydrate from the intestine, we previously determined the amount of unabsorbed carbohydrate after breakfast by the breath hydrogen test in the four seasons. In pursuing our hypothesis further, we also recorded gastric myoelectrical activity before and after the breakfasts. In the current report, we describe the seasonality of gastric myoelectrical activity. Twenty-six Japanese female subjects were studied in winter, spring, summer and autumn. The cutaneous electrogastrogram was analysed by spectral analysis to compute the pre- and post-prandial dominant slow wave frequency (DF), and percentage of the 2 - 4 cpm gastric slow wave (Normal %). Two-factor ANOVA indicated that there was no significant seasonal variation in DF and Normal %. These results indicate that seasonal variations in digestion and absorption of dietary carbohydrate are caused by factors other than gastric and small intestinal motility.     

Seasonal and species variation in the content of cadmium and associated metals in pasture plants at Shipham

Summary Very high Cd and Zn concentrations exist in soils reclaimed from old mine workings at Shipham but little of the metal is transferred into the pasture herbage. The amount of metal in the soil therefore only influences the amount in the aerial part of the plant to a small degree. It would appear to be the plant species which to a large extent governs its metal burden: grasses accumulating the least Cd and members of the Compositae the most.Within this species variation exists a change in metal content that corresponds to the time of year, setal levels in plants peaking in the winter between January and March. This increase in the metal content of the shoot reflects the redistribution of metal previously bound within the root. The movement of Pb may be associated with changes in the phosphate status of the plant. In grasses it would appear that the root possesses the highest metal burden, and forHolcus lanatus, tolerance to both Cd and Zn has been established. The ammonium-acetate and DTPA-extractable Zn/Cd ratio in soils corresponds closely to that found in the roots of both ryegrass and Yorkshire fog. A much higher ratio was observed in the shoots of these plants.     

Seasonal variation of denitrification rate in Lake Suwa sediment

The seasonal variation of denitrification rate in sediments in the central station of Lake Suwa, Japan, was estimated by the acetylene-inhibition technique from March 20 to December 10, 1994. The denitrification rate ranged from 0 to 1800µmolNm^–2day^–1 and showed a distinct seasonal trend, i.e., relatively high rates in spring and winter, and low or negligible rates in summer. The denitrification rate was well correlated with NO^–₃ concentration in overlying water, suggesting that NO^–₃ in overlying water was the primary controlling factor for denitrification. The annual rate of denitrification was 0.15molNm^–2year^–1. Denitrification removed 5% of the annual nitrogen load from the lake, and this fraction was relatively small compared to the values reported for a variety of aquatic environments. In Lake Suwa, NO^–₃ in the water column was depleted during summer, and this suppressed effective removal of nitrogen from the lake by denitrification.     

Drought causes reduced growth of trembling aspen in western Canada

Adequate and advance knowledge of the response of forest ecosystems to temperature‐induced drought is critical for a comprehensive understanding of the impacts of global climate change on forest ecosystem structure and function. Recent massive decline in aspen‐dominated forests and an increased aspen mortality in boreal forests have been associated with global warming, but it is still uncertain whether the decline and mortality are driven by drought. We used a series of ring‐width chronologies from 40 trembling aspen (Populus tremuloides Michx.) sites along a latitudinal gradient (from 52° to 58°N) in western Canada, in an attempt to clarify the impacts of drought on aspen growth by using Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI). Results indicated that prolonged and large‐scale droughts had a strong negative impact on trembling aspen growth. Furthermore, the spatiotemporal variability of drought indices is useful for explaining the spatial heterogeneity in the radial growth of trembling aspen. Due to ongoing global warming and rising temperatures, it is likely that severer droughts with a higher frequency will occur in western Canada. As trembling aspen is sensitive to drought, we suggest that drought indices could be applied to monitor the potential effects of increased drought stress on aspen trees growth, achieve classification of eco‐regions and develop effective mitigation strategies to maintain western Canadian boreal forests.     

Intraspecific variation in aspen phytochemistry: effects on performance of gypsy moths and forest tent caterpillars

Individual quaking aspen trees vary greatly in foliar chemistry and susceptibility to defoliation by gypsy moths and forest tent caterpillars. To relate performance of these insects to differences in foliar chemistry, we reared larvac from egg hatch to pupation on leaves from different aspen trees and analyzed leaf samples for water, nitrogen, total nonstructural carbohydrates, phenolic glycosides, and condensed tannins. Larval performance varied markedly among trees. Pupal weights of both species were strongly and inversely related to phenolic glycoside concentrations. In addition, gypsy moth performance was positively related to condensed tannin concentrations, whereas forest tent caterpillar pupal weights were positively associated with leaf nitrogen concentrations. A subsequent study with larvae fed aspen leaves supplemented with the phenolic glycoside tremulacin confirmed that the compound reduces larval performance. Larvae exhibited increased stadium durations and decreased relative growth rates and food conversion efficiencies as dietary levels of tremulacin increased. Differences in performance were more pronounced for gypsy moths than for forest tent caterpillars. These results suggest that intraspecific variation in defensive chemistry may strongly mediate interactions between aspen, gypsy moths and forest tent caterpillars in the Great Lakes region, and may account for differential defoliation of aspen by these two insect species.     

Effects of elevated atmospheric CO2 and tropospheric O3 on nutrient dynamics: decomposition of leaf litter in trembling aspen and paper birch communities

Atmospheric changes could strongly influence how terrestrial ecosystems function by altering nutrient cycling. We examined how the dynamics of nutrient release from leaf litter responded to two important atmospheric changes: rising atmospheric CO₂ and tropospheric O₃. We evaluated the independent and combined effects of these gases on foliar litter nutrient dynamics in aspen (Populus tremuloides Michx) and birch (Betula papyrifera Marsh)/aspen communities at the Aspen FACE Project in Rhinelander, WI. Naturally senesced leaf litter was incubated in litter bags in the field for 735 days. Decomposing litter was sampled six times during incubation and was analyzed for carbon, and both macro (N, P, K, S, Ca, and Mg) and micro (Mn, B, Zn and Cu) nutrient concentrations. Elevated CO₂ significantly decreased the initial litter concentrations of N (−10.7%) and B (−14.4%), and increased the concentrations of K (+23.7%) and P (+19.7%), with no change in the other elements. Elevated O₃ significantly decreased the initial litter concentrations of P (−11.2%), S (−8.1%), Ca (−12.1%), and Zn (−19.5%), with no change in the other elements. Pairing concentration data with litterfall data, we estimated that elevated CO₂ significantly increased the fluxes to soil of all nutrients: N (+12.5%), P (+61.0%), K (+67.1%), S (+28.0%), and Mg (+40.7%), Ca (+44.0%), Cu (+38.9%), Mn (+62.8%), and Zn (+33.1%). Elevated O₃ had the opposite effect: N (−22.4%), P (−25.4%), K (−27.2%), S (−23.6%), Ca (−27.6%), Mg (−21.7%), B (−16.2%), Cu (−20.8%), and Zn (−31.6%). The relative release rates of the nine elements during the incubation was: K ≥ P ≥ mass ≥ Mg ≥ B ≥ Ca ≥ S ≥ N ≥ Mn ≥ Cu ≥ Zn. Atmospheric changes had little effect on nutrient release rates, except for decreasing Ca and B release under elevated CO₂ and decreasing N and Ca release under elevated O₃. We conclude that elevated CO₂ and elevated O₃ will alter nutrient cycling more through effects on litter production, rather than litter nutrient concentrations or release rates.     

Seasonal variation of vesicular-arbuscular mycorrhizae in eroded soils from southern Spain

A survey was carried out of the seasonal variations in the number of spores in the soil and of the percentage of root infection. The stage of development of the host plants, environmental variations and physicochemical characteristics of the soil were taken into account. Fifteen plants valid as forage and adaptable to semi-arid conditions and poor soils were selected. In general, the maximum spore density was reached in the fruit-bearing period of the plants. It remained high during autumn, fell to a minimum in winter and tended to increase in spring. Root infection was at a maximum when the plants flowered, after which it decreased to a minimum in summer.     

Seasonal variation of dissolved aluminum concentration in harmonic-type Lake Biwa, Japan

Monthly observations performed on a typical harmonic-type lake, Lake Biwa (latitude 35°15′ N, longitude 136°05′ E, Japan), showed that the particulate aluminum concentration varied around a mean value of 0.8 μM, with occasional extraordinarily high values, whereas the dissolved aluminum concentration varied, in the surface layer of the whole lake, between a minimum of 0.01 μM and a maximum of 0.30 μM, depending on the season. Although the variation in dissolved aluminum paralleled the variation in the pH of the lake water, the variation in dissolved aluminum lagged behind the variation in pH by approximately 1 month. A series of laboratory incubation experiments suggested that the supply of dissolved aluminum from, and its removal by, the suspended particulate matter involved a slow, pH-dependent reaction. The stoichiometry and the apparent equilibrium constant of this reaction were evaluated by adopting a zeolite-like structure for the surfaces of the suspended particulates. Received: December 28, 2000 / Accepted: August 22, 2001     

Microsatellite DNA somaclonal variation in micropropagated trembling aspen (Populus tremuloides)

Microsatellite DNA markers of ten simple sequence repeat (SSR) loci were used to examine somaclonal variation in randomly selected micropropagated plantlets derived from three different Populus tremuloides donor trees (genotypes). The plantlets were obtained from tissue cultures of dormant vegetative buds, and those derived from the same donor tree, grown in the greenhouse, did not exhibit any sign of visible morphological variation. No microsatellite DNA variation was observed among 13 somaclones of one tree and 4 somaclones of another tree at eight of the ten SSR loci. However, despite the small number of micropropagated progeny per tree sampled, microsatellite DNA variation was detected among the plantlets derived from the same donor trees at two SSR loci. The primer pair for the SSR locus PTR5 revealed somaclonal variation in 1 out of the 13 plantlets obtained from one genotype, while the primer pair for the PTR2 SSR locus revealed somaclonal variation in one out of the four plantlets obtained from another genotype. The variation at the PTR2 locus resulted in the appearance of a new allele of increased size, possibly due to an addition of the repeat units, while the variation at the PTR5 locus resulted in the appearance of third allele, presumably due to the presence of a single extra chromosome or duplication of a chromosomal segment. These results demonstrate that the genetic fidelity of micropropagated plants of P. tremuloides cannot always be assured and somaclonal variation can occur even when tissues of well organized vegetative buds are used for tissue cultures; that somaclonal variation cannot always be detected at the gross morphological level; and that microsatellite DNA markers provide useful and sensitive markers for determining the clonal fidelity and somaclonal variation in P. tremuloides.     

Seasonal and age-related variation in the needle quality of five conifer species

Summary Age changes of foliage resource quality (water, nitrogen, fibre, phenolics and toughness) were studied in five species of conifer (Pinus sylvestris L.), Picea abies (L.) Karsten, Tsuga heterophylla (Rafinesque) Sargent (all Pinaceae), Chamaecyparis lawsonian (Murray) Parlatore and Thuja plicata D. Don (both Cupressaceae) over a 2-year period in an English forest.Mature foliage of Pinus sylvestris was characterized by higher levels of nitrogen, fibre and toughness, and lower phenolics, and that of Tsuga heterophylla by higher levels of phenolics, and lower fibre and toughness levels, than the mature needles of the other species studied. Immature needles had higher levels of water and nitrogen, and lower levels of fibre and toughness, than older needles. Immature needles of Picea abies and Tsuga heterophylla had a high concentration of phenolics, which decreased with needle maturity. By mid-August, the levels of most of the foliar constituents in current-year needles had stabilized at levels maintained for the next year. Sampling revealed a fall in the concentration of phenolics, fibre and water in mature needles between March and June. Possible reasons for this seasonal trend are discussed. The levels of conifer foliar constituents were compared with levels recorded in broadleaf trees. Conifers had greater concentrations of all measured foliar constituents, but, with the exception of the six fold greater toughness of conifer needles, the differences between broadleaves and conifers were less than those between the immature and mature conifer needles. Previous studies have related the abundance of Lepidoptera on conifers to hostplant taxonomic relationships. However, the foliar constituents measured in this study were poor predictors of taxonomic relationships between the conifers. It is suggested that the abundance of Lepidoptera on conifers is not determined by levels of general foliar constituents and the role of other hostplant factors in shaping lepidopteran utilization of conifers is discussed.     

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.     

Seasonal variation in primary production of microphytobenthos at the Isshiki intertidal flat in Mikawa Bay

Seasonal variations in photosynthetic rates by microphytobenthos and phytoplankton at the Isshiki tidal flat in Mikawa Bay were measured with a ¹⁴C combustion method. In addition, diurnal variations in the photosynthetic rate and photosynthesis versus irradiance (P-I) curves were obtained through in situ incubation. The photosynthetic rate of microphytobenthos (annual average, 13.9 ± 6.4 mg C m⁻² h⁻¹) did not show a remarkable change, and they maintained a higher production rate than phytoplankton (annual average 9.0 ± 5.1 mg C m⁻² h⁻¹) throughout the year. The P-I curves from in situ experiments showed that the photosynthetic activity of microphytobenthos at the laboratory irradiance (250 μE m⁻² s⁻¹) was 56% of that at the maximum irradiance (1200 μE m⁻² s⁻¹) in situ. In the in situ experiments, the chlorophyll a concentration, photosynthetic rate, and activity of microphytobenthos varied greatly throughout the day, influenced by tidal submersion/emersion and daylight. From an analysis of these results, it is considered that microphytobenthos contributed greatly to primary production in this ecosystem throughout the year by adapting suitably to intertidal environments. Received: July 28, 1999 / Accepted: October 10, 1999     

Seasonal variation in effect of spa therapy on chronic pain

This study sought to investigate whether the effects of spa therapy are subject to seasonal variation as suggested by conventional spa therapy research. A total of 268 female (age 31–90 yr) and 119 male (age 35–85 yr) patients with noninflammatory chronic pain were studied. Patients stayed at an Austrian spa for 3 wk and received 2–4 treatments per day, including mudpacks, massages, and exercise therapy. In different groups of patients for 2 yr, pain (self-assessed by questionnaire and Likert scales) and associated variables (mood, fatigue) were measured at the beginning, end, and 6 wk after spa therapy. Data were analyzed by multivariate analysis of covariance controlling for possible group differences between seasons and cosinor analysis. The effect of spa therapy on pain was seasonally dependent; short-term decrease of pain was best between April and June and medium-term decrease of pain was best between October and November, with a second minor peak in fall and spring, respectively. The magnitude of the seasonal variation was greater for back (～30%) than for joint (～20%) pain. Positive mood also improved most between April and June. The observed semi-annual variations of pain do not correspond to the well-known annual change in many physiological and psychological variables. The results suggest that the effects of spa therapy and possibly other related treatments, such as physical and alternative therapies, are subject to seasonal variation.     

Seasonal variation in effect of spa therapy on chronic pain

This study sought to investigate whether the effects of spa therapy are subject to seasonal variation as suggested by conventional spa therapy research. A total of 268 female (age 31-90 yr) and 119 male (age 35-85 yr) patients with noninflammatory chronic pain were studied. Patients stayed at an Austrian spa for 3 wk and received 2-4 treatments per day, including mudpacks, massages, and exercise therapy. In different groups of patients for 2 yr, pain (self-assessed by questionnaire and Likert scales) and associated variables (mood, fatigue) were measured at the beginning, end, and 6 wk after spa therapy. Data were analyzed by multivariate analysis of covariance controlling for possible group differences between seasons and cosinor analysis. The effect of spa therapy on pain was seasonally dependent; short-term decrease of pain was best between April and June and medium-term decrease of pain was best between October and November, with a second minor peak in fall and spring, respectively. The magnitude of the seasonal variation was greater for back (∼30%) than for joint (∼20%) pain. Positive mood also improved most between April and June. The observed semi-annual variations of pain do not correspond to the well-known annual change in many physiological and psychological variables. The results suggest that the effects of spa therapy and possibly other related treatments, such as physical and alternative therapies, are subject to seasonal variation.     

Seasonal variation of necrospermia in man

Abstract

We have investigated the variability of the necrozoospermia in human semen, over three periods of nine months from the end of October to July, during the last three years. The donors are twenty young men in good health who have given regular specimens of sperm once of twice monthly for a period of only one or two years. Analysis of the mean curves shows a maximum during winter and a minimum in the beginning of spring, for the three years considered.     

Seasonal and intradiurnal variation of allergenic fungal spores in urban and rural areas of the North of Portugal

Because fungal spore emission intensity varies throughout the year and even throughout the day, study of the hourly distribution is an important aspect of aerobiological monitoring. The objective of this work was to determine seasonal and intradiurnal variation of allergenic airborne fungal spores in urban and rural areas. The aerobiological study was performed from 2005 to 2007 using Hirst-type volumetric spore traps. Fungal spore types (Cladosporium, Alternaria, and Aspergillus/Penicillium) were selected according to their allergenic capacity and their frequency in the atmosphere. Cladosporium was the most frequent fungal spore in both locations, together with Alternaria; its concentration was higher during summer whereas Aspergillus/Penicillium was more abundant during autumn. Alternaria and Cladosporium maximum daily spore concentration was reached from 16.00 to 20.00 h. Aspergillus/Penicillium spore distribution differed in the two locations, and although it was difficult to establish a distribution pattern the highest concentration were found during the night. Determination of periods of high concentration may help allergic patients to avoid the daily periods when the allergen concentration is highest.     

Seasonal variation of the chemical constituents of the essential oil of Santolina etrusca from Italy

The seasonal variation of the essential oil, in terms of both yield and composition, of a population of Santolina etrusca (Asteraceae) is reported in detail for different aerial parts, including sterile branches, fertile branches, and capitula. The yields generally increased from November to June, and then decreased in August and September. The main constituents of the sterile branches were 1,8-cineole and viridiflorol. The oil from fertile branches was characterized by myrcene as principal compound, whereas the essential oil obtained from the capitula contained germacrene D as the main constituent. Several compounds, as identified by GC and GC/MS, were found to prevail during the cold season.     

Seasonal variation in toxic steroidal alkaloids of foothill death camas (Zigadenus paniculatus)

Death camas (Zigadenus spp.) is a common poisonous plant in North America with plants occurring in a wide variety of habitats with species of toxic concern occurring primarily in meadows, grasslands, shrublands, and mountains. The toxicity of Zigadenus species has been attributed to a series of steroidal alkaloids. The objective of this study was to evaluate zygacine and total steroidal alkaloid concentrations in different plant tissues of Zigadenus paniculatus as a function of plant maturity. Death camas plants were collected at two locations at different developmental growth stages representing vegetative, flower, seed pod, and shattered seed pod stages. Zygacine represented greater than 50% of the total steroidal alkaloids at all developmental stages. In bulbs, total steroidal alkaloid and zygacine concentrations did not change significantly as a function of plant phenology, and concentrations were lower than what were observed in above ground plant parts. Total steroidal alkaloid and zygacine concentrations in above ground parts were highest at early vegetative growth stages and decreased over the growing season. In plant reproductive parts, total steroidal alkaloid and zygacine concentrations increased until maturity and then decreased as the plant senesced. The concentrations of steroidal alkaloids reported here suggest that the toxic risk associated with death camas is greatest in the early vegetative growth stages followed by the flower and pod stages. There is a toxic risk to livestock as long as the plant is present, and caution should be taken when grazing livestock in areas with death camas until the plant senesces.     

Seasonal variation of 1,25-dihydroxyvitamin D and its association with body mass index and age

Under most normal conditions the serum level of 1,25-dihydroxyvitamin D is constant throughout the year, due to tight biochemical regulation. In contrast to this, the level of 25-hydroxyvitamin D is variable through the year, being largest in late summer, due to photosynthesis in the skin. The vitamin D status is usually assessed by measuring the level of the latter vitamin D derivative, rather than that of the presumably most active derivative 1,25(OH)₂ vitamin D.We here show that for persons with a high body mass index (BMI) there is a significant seasonal variation, not only of 25(OH) vitamin D, but also of 1,25(OH)₂ vitamin D. The variation seems to be largest for those with the poorest vitamin D status. Furthermore, there seems to be a correlation between the levels of the two vitamin D metabolites, indicating that the regulation of 1,25(OH)₂ vitamin D is not always tight, notably in persons with high BMI.     

Growth and chemical responses of trembling aspen to simulated browsing and ungulate saliva

Aims Woody plant-browser systems represent an understudied facet of herbivory. We subjected four genotypes of trembling aspen to artificial browsing, similar to that of a large mammalian herbivore, and applied deer saliva to clipped and unclipped trees to assess: (i) the effects of artificial browsing on aspen growth and phytochemistry of leaves and stems, (ii) genotypic variation in responses and (iii) potential alterations of responses by mammalian saliva.Methods Potted aspen trees were grown outdoors on the University of Wisconsin-Madison campus. The experiment consisted of a fully-crossed, 2 × 2 × 4 randomized complete block design, with two levels of artificial browsing (unclipped and clipped), two levels of saliva application (no saliva and saliva) and four aspen genotypes. To simulate ungulate browsing damage, we removed the upper 50% of the stem of half of the trees by pinching the stem with needle-nosed pliers and then separating it by tearing. For half of the damaged trees, we immediately swabbed the wound with deer saliva. Trees in the unclipped plus saliva treatment were swabbed with saliva at the 50% height mark. To assess the effects of clipping and saliva application, we harvested all trees after 2 months and measured various growth and chemical properties. Growth measurements included height, vertical growth, mass of leaves, stems and roots, leaf number and area and bud set. Chemical parameters included defensive, nutritional and structural components of both foliage and stems.Important findings Clipping affected most of the growth parameters measured, decreasing tree height, leaf, stem, root and total tree mass and leaf area. Clipped trees had greater vertical growth, more leaves and higher specific leaf area (SLA) than unclipped trees. Deer saliva had little to no effect on plant growth response to the clipping treatment. Terminal budset was delayed by clipping and varied among genotypes but not in response to saliva application. Clipping also affected most of the phytochemical variables measured, reducing defensive compounds (phenolic glycosides and condensed tannins (CTs)) and nutrients (N), but increasing structural components (cellulose and lignin) in both leaves and stems. Saliva had very little effect on tree chemistry, causing only a slight decrease in the amount of CTs in leaves. In general, leaves contained more defensive compounds and nutrients, but much less cellulose, compared with stems. Genotypes differed for all physical and chemical indices, and in tolerance to damage as measured by vertical growth. In addition, for most of the physical and chemical variables measured, genotype interacted with the clipping treatment, suggesting that in natural stands some genotypes will resist or tolerate browsing better than others, affecting forest genetic composition and ultimately forest dynamics.