CD133<Superscript>+</Superscript>CD44<Superscript>+</Superscript> subgroups may be human small intestinal stem cells

The identification and separation of small intestinal epithelial stem cells are still on the preliminary stage. In this study, we planned to utilize immunohistochemistry, fluorescence-activated cell sorting (FACS) and RT-PCR to investigate the possibility of CD133 and CD44 as markers of human small intestinal epithelial stem cells. The expressions of CD133, CD44 and Lgr5 were studied by immunohistochemistry. Four subgroups of CD133⁺CD44⁺, CD133⁺CD44⁻, CD133⁻CD44⁺, CD133⁻CD44⁻ were sorted out through FACS and the expression level of Lgr5 gene was measured by RT-PCR and polyacrylamide gel electropheresis (PAGE) with sliver stained. Ten cases of samples were available for analyzing. By immunohistochemical staining, few cells with positive expressions of CD133, CD44 and Lgr5 were distributed in the bottom of crypts with the expression locations somewhat overlapped. The average percentage of CD133⁺CD44⁺ cells was 0.0580 ± 0.0403%, while the corresponding contents of CD133⁺CD44⁻ cells, CD133⁻CD44⁺ cells and CD133⁻CD44⁻ cells were 0.4000 ± 0.1225%, 0.7000 ± 0.2646% and 76.5600 ± 3.5529% respectively. Ten times of positive expressions of Lgr5 were detected in the CD133⁺CD44⁺ groups, while 9/10, 8/10 and 4/10 times for CD133⁺CD44⁻, CD133⁻CD44⁺ and CD133⁻CD44⁻ subgroups respectively. With the help of Quantityone 4.62 software, the densities of corresponding place to Lgr5 and reference gene were obtained. The density ratios of corresponding place to Lgr5 to reference gene were significant difference between subgroups (P < 0.001). By means of LSD method, the density ratios in CD133⁺CD44⁺ subgroups had statistical differences from the other subgroups (P < 0.05). We concluded CD133⁺CD44⁺ cells may be human small intestinal epithelial stem cells, which need further researches to confirm.     

Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> exchange activity in the alkaliphile halotolerant cyanobacterium <Emphasis Type="Italic">Aphanothece halophytica</Emphasis>

The activity of Na⁺/H⁺ exchanger to remove toxic Na⁺ is important for growth of organisms under high salinity. In this study, the halotolerant cyanobacterium Aphanothece halophytica was shown to possess Na⁺/H⁺ exchange activity since exogenously added Na⁺ could dissipate a pre-formed pH gradient, and decrease extracellular pH. Kinetic analysis yielded apparent K _m (Na⁺) and V _max of 20.7 ± 3.1 mM and 3,333 ± 370 nmol H⁺ min⁻¹ mg⁻¹, respectively. For cells grown under salt-stress condition, the apparent K _m (Na⁺) and V _max was 18.3 ± 3.5 mM and 3,703 ± 350 nmol H⁺ min⁻¹ mg⁻¹, respectively. Three cations with decreasing efficiency namely Li⁺, Ca²⁺, and K⁺ were also able to dissipate pH gradient. Only marginal exchange activity was observed for Mg²⁺. The exchange activity was strongly inhibited by Na⁺-gradient dissipators, monensin, and sodium ionophore as well as by CCCP, a protonophore. A. halophytica showed high Na⁺/H⁺ exchange activity at neutral and alkaline pH up to pH 10. Cells grown at pH 7.6 under high salinity exhibited higher Na⁺/H⁺ exchange activity than those grown under low salinity during 15 days of growth suggesting a role of Na⁺/H⁺ exchanger for salt tolerance in A. halophytica. Cells grown at alkaline pH of 9.0 also exhibited a progressive increase of Na⁺/H⁺ exchange activity during 15 days of growth.     

Isotopic signature (<Superscript>15</Superscript>N/<Superscript>14</Superscript>N and <Superscript>13</Superscript>C/<Superscript>12</Superscript>C) confirms similarity of trophic niches of millipedes (Myriapoda,diplopoda) in a temperate deciduous forest

The species composition, abundance, and isotopic signature of millipedes (Myriapoda, Diplopoda) were investigated in seven biotopes of Kaluzhskie Zaseki State Nature Reserve. Nine Diplopoda species were found in total, and the local species diversity (within a sampling plot) reached seven species. The Diplopoda tissues were similar to the plant litter in the isotopic composition of nitrogen (δ¹⁵N was by 0.4‰ higher, on average), but were strongly enriched in heavy carbon (δ¹³C was by 4‰ higher, on average). Removal of mineral carbon from the cuticle reduced δ¹³C of Diplopoda by about 1.4‰ on average. Differences in the δ¹⁵N and δ¹³C values between the species did not exceed 2.5‰. Differences in the isotopic compositions of the considered species were small, and, it is impossible to distinguish particular trophic guilds in the Diplopoda community. Analysis of the published data confirmed that isotopic differentiation of millipedes was much less pronounced than in other investigated groups of soil animals. Hence, millipedes of the deciduous forest form a uniform trophic group.     

Effect of Resting Patterns of Tamarins (<Emphasis Type="BoldItalic">Saguinus fuscicollis</Emphasis> and <Emphasis Type="BoldItalic">Saguinus mystax</Emphasis>) on the Spatial Distribution of Seeds and Seedling Recruitment

The spatial distributions of dispersed seeds have important evolutionary consequences for plants. Repeated defecations in sites frequently used by seed dispersers can result in high seed concentrations. We observed the resting behavior of a mixed-species group of tamarins in Peru and recorded the occurrence of seed dispersal (over 8 mo) and seed fate (over 11–22 mo) to determine whether the location and use of resting sites influenced the spatial distribution of dispersed seeds and seedlings. The tamarins rested mostly on trees (Saguinus fuscicollis: 60.6%, S. mystax: 89.2%) and dead trunks (S. fuscicollis: 24.4%) and used 61% of their resting sites repeatedly. During both the dry and wet seasons, tamarins dispersed significantly more seeds within resting areas (0.00662 and 0.00424 seeds/m², respectively) than outside them (0.00141 and 0.00181 seeds/m²). Seed survival and seedling recruitment did not differ significantly between resting and other areas, resulting in a higher seedling concentration around the resting sites. Seed density did not increase with the duration or the frequency of use of the resting sites but did increase when we pooled the seasonal resting sites together in 50 m × 50 m quadrats, ultimately causing a clumped distribution of dispersed seeds. The use of resting sites in secondary forest, particularly during the dry season, allows the creation of seedling recruitment centers for species coming from the primary forest. Our findings show that tamarin resting behavior affects the spatial distribution of dispersed seeds and seedlings, and their resting sites play an important role in plant diversity maintenance and facilitate forest regeneration in degraded areas.     

灵山湾国家森林公园垂序商陆土壤种子库时空动态及其对防除措施的响应

土壤种子库是植物潜在的种群,对生态系统稳定和未来植被的结构、功能有着举足轻重的影响。垂序商陆(Phytolacca americana)的入侵已对山东省胶南市灵山湾国家森林公园的森林生态系统构成严重危害。为调查该物种在公园内的潜在扩散能力,于2009—2014年调查了刺槐(Robinia pseudoacacia)林、黑松(Pinus thunbergii)林、刺槐黑松混交林和紫穗槐(Amorpha fruticosa)林(灌丛)4种林分类型,以及2009年采用物理和化学控制入侵危害严重的刺槐林内的土壤种子库。结果表明:垂序商陆种子在4种林分中均有发现,在刺槐、黑松林内表现为由林缘至林内逐步降低的趋势。垂序商陆种子只存在于枯落物层和5 cm以上的土壤中,随土层深度的增加而减少,枯落物层土壤种子库由林缘到林内呈递减趋势。与2009年相比,2014年黑松林和灌丛中平均种子库密度分别降低46%和44%,刺槐林和混交林分别增加299%和355%。垂序商陆种子发芽率在10%以下,随土层深度的增加而依次降低。采用物理、化学控制措施的刺槐林内垂序商陆的更新量、结实量、种子库含量均明显高于紫穗槐林的。调查结果表明垂序商陆土壤种子库具有明显的空间异质性,并且保持了较强的繁殖潜力,营造紫穗槐灌丛可以有效控制垂序商陆的扩散,可为经营沿海防护林提供理论指导。     

Subsurface CO<Subscript>2</Subscript> Dynamics in Temperate Beech and Spruce Forest Stands

Rates of soil respiration (CO₂ effluxes), subsurface pore gas CO₂/O₂ concentrations, soil temperature and soil water content were measured for 15 months in two temperate and contrasting Danish forest ecosystems: beech (Fagus sylvatica L.) and Norway spruce (Picea abies [L.] Karst.). Soil CO₂ effluxes showed a distinct seasonal trend in the range of 0.48–3.3 μmol CO₂ m⁻² s⁻¹ for beech and 0.50–2.92 μmol CO₂ m⁻² s⁻¹ for spruce and were well-correlated with near-surface soil temperatures. The soil organic C-stock (upper 1 m including the O-horizon) was higher in the spruce stand (184±23 Mg C ha⁻¹) compared to the beech stand (93±19 Mg C ha⁻¹) and resulted in a faster turnover time as calculated by mass/flux in soil beneath the beech stand (28 years) compared to spruce stand (60 years). Observed soil CO₂ concentrations and effluxes were simulated using a Fickian diffusion-reaction model based on vertical CO₂ production rates and soil diffusivity. Temporal trends were simulated on the basis of observed trends in the distribution of soil water, temperature, and live roots as well as temperature and water content sensitivity functions. These functions were established based on controlled laboratory incubation experiments. The model was successfully validated against observed soil CO₂ effluxes and concentrations and revealed that temporal trends generally could be linked to variations in subsurface CO₂ production rates and diffusion over time and with depths. However, periods with exceptionally high CO₂ effluxes (> 20 μmol CO₂ m⁻² s⁻¹) were noted in March 2000 in relation to drying after heavy rain and after the removal of snow from collars. Both cases were considered non-steady state and could not be simulated.     

Dynamics of <Superscript>18</Superscript>O Incorporation from H <Subscript>2</Subscript><Superscript>18</Superscript>O into Soil Microbial DNA

Heavy water (H₂¹⁸O) has been used to label DNA of soil microorganisms in stable isotope probing experiments, yet no measurements have been reported for the ¹⁸O content of DNA from soil incubated with heavy water. Here we present the first measurements of atom% ¹⁸O for DNA extracted from soil incubated with the addition of H₂¹⁸O. Four experiments were conducted to test how the atom% ¹⁸O of DNA, extracted from Ponderosa Pine forest soil incubated with heavy water, was affected by the following variables: (1) time, (2) nutrients, (3) soil moisture, and (4) atom% ¹⁸O of added H₂O. In the time series experiment, the atom% ¹⁸O of DNA increased linearly (R ² = 0.994, p < 0.01) over the first 72 h of incubation. In the nutrient addition experiment, there was a positive correlation (R ² = 0.991, p = 0.006) between the log₁₀ of the amount of tryptic soy broth, a complex nutrient broth, added to soil and the log₁₀ of the atom% ¹⁸O of DNA. For the experiment where soil moisture was manipulated, the atom% ¹⁸O of DNA increased with higher soil moisture until soil moisture reached 30%, above which ¹⁸O enrichment of DNA declined as soils became more saturated. When the atom% ¹⁸O for H₂O added was varied, there was a positive linear relationship between the atom% ¹⁸O of the added water and the atom% ¹⁸O of the DNA. Results indicate that quantification of ¹⁸O incorporated into DNA from H₂¹⁸O has potential to be used as a proxy for microbial growth in soil.     

Measurement of activity concentrations of <Superscript>40</Superscript>K, <Superscript>226</Superscript>Ra and <Superscript>232</Superscript>Th for assessment of radiation hazards from soils of the southwestern region of Nigeria

Activity concentrations of the selected radionuclides ⁴⁰K, ²²⁶Ra and ²³²Th were measured in surface soil samples collected from 38 cities in the southwest region of Nigeria by means of gamma spectroscopy with a high-purity germanium detector. Measured activity concentration values of ⁴⁰K varied from 34.9 ± 4.4 to 1,358.6 ± 28.5 Bq kg⁻¹ (given on a dry mass (DM) basis) with a mean value of 286.5 ± 308.5 Bq kg⁻¹; that of ²²⁶Ra varied from 9.3 ± 3.7 to 198.1 ± 13.8 Bq kg⁻¹ with a mean value of 54.5 Bq kg⁻¹ and a standard deviation of 38.7 Bq kg⁻¹, while that of ²³²Th varied from 5.4 ± 1.1 to 502.0 ± 16.5 Bq kg⁻¹ with a mean value of 91.1 Bq kg⁻¹ and standard deviation of 100.9 Bq kg⁻¹. The mean activity concentration values obtained for ²²⁶Ra and ²³²Th are greater than the world average values reported by the United Nations Scientific Committee on Effects of Atomic Radiation for areas of normal background radiation. Radiological indices were estimated for the radiation/health hazards of the natural radioactivity of all soil samples. Estimated absorbed dose rates in air varied from 12.42 ± 2.25 to 451.33 ± 19.06 nGy h⁻¹, annual outdoor effective dose rates from 0.015 ± 0.003 to 0.554 ± 0.023 mSv year⁻¹, internal hazard index from 0.10 ± 0.03 to 3.02 ± 0.16, external hazard index from 0.07 ± 0.01 to 2.60 ± 0.11, representative level index from 0.19 ± 0.03 to 6.84 ± 0.29, activity index from 0.09 ± 0.02 to 3.42 ± 0.15, and radium equivalent activity from 26.95 ± 5.04 to 963.15 ± 41.87 Bq kg⁻¹. Only the mean value of the representative level index exceeds the limit for areas of normal background radiation. All other indices show mean values that are lower than the recommended limits.     

Anti-cyanobacterial activity of <Emphasis Type="Italic">Moringa oleifera</Emphasis> seeds

Filtrates from crushed Moringa oleifera seeds were tested for their effects on growth and Photosystem II efficiency of the common bloom-forming cyanobacterium Microcystis aeruginosa. M. aeruginosa populations exhibited good growth in controls and treatments with 4- and 8-mg crushed Moringa seeds per liter, having similar growth rates of 0.50 (±0.01) per day. In exposures of 20- to 160-mg crushed Moringa seeds L⁻¹, growth rates were negative and on average −0.23 (±0.05) .day⁻¹. Presumably, in the higher doses of 20- to 160-mg crushed seeds per liter, the cyanobacteria died, which was supported by a rapid drop in the Photosystem II efficiency (Φ_PSII), while the Φ_PSII was high and unaffected in 0, 4, and 8 mg L⁻¹. High-density populations of M. aeruginosa (chlorophyll-a concentrations of ∼270 μg L⁻¹) were reduced to very low levels within 2 weeks of exposure to ≥80-mg crushed seeds per liter. At the highest dosage of 160 mg L⁻¹, the Φ_PSII dropped to zero rapidly and remained nil during the course of the experiment (14 days). Hence, under laboratory conditions, a complete wipeout of the bloom could be achieved. This is the first study that yielded evidence for cyanobactericidal activity of filtrate from crushed Moringa seeds, suggesting that Moringa seed extracts might have a potential as an effect-oriented measure lessening cyanobacterial nuisance.     

Theoretical study of isotope effects on the stereodynamics of H<Superscript>+</Superscript>+HD and its isotopic variant D<Superscript>+</Superscript>+HD

The stereodynamics for H⁺+HD and its isotopic variant D⁺+HD were studied with a quasi-classical trajectory (QCT) method at a collision energy of 0.7 eV on the ground 1¹A′ potential energy surface (PES). The polarization-dependent differential cross-sections (PDDCSs) in the center-of-mass frame are presented here. Furthermore, the distribution of the angle between k and j′, p(θ _r ) and the distribution of the dihedral angle p(ϕ _r ) were calculated and are discussed. The results indicate that isotopic substitution exerts substantial effects on the differential cross-section and the product’s rotational polarization.     

Mechanisms of plant regeneration during succession after shifting cultivation in eastern Amazonia

The role of seed bank, seed rain, and regeneration from seedlings and sprouts after swidden agriculture was compared in 5-, 10- and 20-year-old secondary forest and in a primary forest in Bragantina, Pará, Brazil. The seed bank (0–5 cm soil depth) was largest in the 5-year-old forest (1190 ± 284 seeds m⁻²) and decreased nearly ten-fold with age to 137 ± 19 seeds m⁻² in the primary forest. The highest seed rain was in the 5-year-old forest (883 ± 230 seeds m⁻² year⁻¹) and the least in the primary forest (220 ± 80 seeds m⁻² year⁻¹). Large plants (≥5 cm dbh) had more individuals and species that regenerated from sprouts than from seeds and the most abundant tree species in the secondary forest stands of all ages appear to be maintained by sprouting. The smaller individuals (≥1 m tall, <5 cm dbh) in the 5-year-old forest were mainly from sprouts, but those in the older secondary forests originated mainly from seeds. These results show that at the beginning of succession, although many species can be introduced to swidden fallow from seed bank and seed rain, it is the sprout that is the main source of recruits of primary forest species in secondary forests in Bragantina.     

Returns from Harvesting a Commercial Non-timber Forest Product and Particular Characteristics of Harvesters and Their Strategies: <Emphasis Type="Italic">Aquilaria crassna</Emphasis> and Agarwood in Lao PDR<Superscript>1</Superscript>

Returns from Harvesting a Commercial Non-timber Forest Product andParticular Characteristics of Harvesters and Their Strategies: Aquilaria crassna and Agarwood in Lao PDR. This paper explores associations between the returns from harvesting a commercial non-timber forest product and particular characteristics of harvesters and their strategies. Data originate from a survey in Laos of the harvest and trade of agarwood, a highly valuable commodity harvested mainly from tree species in the genus Aquilaria. Five groups of harvesters were identified, with considerable differences in returns between them. Foreign harvesters, i.e., ethnic Vietnamese, earned approximately USD 13 per day on average, while nonlocal full-time harvesters earned approximately USD 9, and nonlocal part-time harvesters USD 7 per day. Local people earn approximately USD 5 per day and only USD 4 if harvesting only took place in village forests. Factors observed to determine returns are market access, especially access to national and international markets, and knowledge and experience in trading, harvesting, and the organization of harvesting trips. It is suggested that interventions should be made to address these factors, to level out returns from harvesting, and to increase the share of returns captured by local people.      

Carbon and nitrogen storage in an age-sequence of <Emphasis Type="Italic">Pinus densiflora</Emphasis> stands in Korea

The carbon (C) and nitrogen (N) storage capabilities of Pinus densiflora in six different stand ages (10, 27, 30, 32, 44, and 71 years old) were investigated in Korea. Thirty sample trees were destructively harvested and 12 were excavated. Samples from the above and belowground tree components, coarse woody debris (CWD), forest floor, and mineral soil (0–30 cm) were collected. Tree biomass was highest in the 71-year-old stand (202.8 t ha⁻¹) and lowest in the 10-year-old stand (18.4 t ha⁻¹). C and N storage in the mineral soil was higher in the 71-year-old stand than in the other stands, mainly due to higher soil C and N concentrations. Consequently, the total ecosystem C and N storage (tree+forest floor+CWD+soil) was positively correlated with stand age: increasing from a minimum in the 10 year old stand (18.8 t C ha⁻¹ and 1.3 t N ha⁻¹) to a maximum in the 71-year-old stand (201.4 t C ha⁻¹ and 8.5 t N ha⁻¹). The total ecosystem C storage showed a similar sigmoidal pattern to that of tree C storage as a function of the age-sequence, while N storage in the CWD, forest floor and mineral soil showed no significant temporal trends. Our results provide important insights that will increase our understanding of C and N storage in P. densiflora stands and our ability to predict changes according to stand age in the region.     

Signaling Pathways in the Biphasic Effect of ANG II on Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> Exchanger in T84 Cells

The effect of ANG II on pH_i, [Ca²⁺]_i and cell volume was investigated in T84 cells, a cell line originated from colon epithelium, using the probes BCECF-AM, Fluo 4-AM and acridine orange, respectively. The recovery rate of pH_i via the Na⁺/H⁺ exchanger was examined in the first 2 min following the acidification of pH_i with a NH₄Cl pulse. In the control situation, the pH_i recovery rate was 0.118 ± 0.001 (n = 52) pH units/min and ANG II (10⁻¹² M or 10⁻⁹ M) increased this value (by 106% or 32%, respectively) but ANG II (10⁻⁷ M) decreased it to 47%. The control [Ca²⁺]_i was 99 ± 4 (n = 45) nM and ANG II increased this value in a dose-dependent manner. The ANG II effects on cell volume were minor and late and should not interfere in the measurements of pH_i recovery and [Ca²⁺]_i. To document the signaling pathways in the hormonal effects we used: Staurosporine (a PKC inhibitor), W13 (a calcium-dependent calmodulin antagonist), H89 (a PKA inhibitor) or Econazole (an inhibitor of cytochrome P450 epoxygenase). Our results indicate that the biphasic effect of ANG II on Na⁺/H⁺ exchanger is a cAMP-independent mechanism and is the result of: 1) stimulation of the exchanger by PKC signaling pathway activation (at 10⁻¹² – 10⁻⁷ M ANG II) and by increases of [Ca²⁺]_i in the lower range (at 10⁻¹² M ANG II) and 2) inhibition of the exchanger at high [Ca²⁺]_i levels (at 10⁻⁹ – 10⁻⁷ M ANG II) through cytochrome P450 epoxygenase-dependent metabolites of the arachidonic acid signaling pathway.     

Differential <Superscript>13</Superscript>C Isotopic Discrimination in Maize at Varying Water Stress and at Low to High Nitrogen Availability

The relationships between ¹³C isotopic discrimination and water stress are well documented for C₃ and C₄ plants. However, the application in the field is hampered by complex interaction patterns with other common stress factors, such as nutrient deficiency. In addition, questions arise if temporal reductions in water availability during crop growth can be traced back using δ¹³C data in the field. The objective of this study therefore is to assess the potential use of δ¹³C observations to quantify water stress and its dynamics in maize (Zea mays L.) grown under low to high nitrogen availability, and to develop tools based on δ¹³C values for its diagnosis in the field. In a pot experiment, carried out in a screen house in Ibadan, Nigeria, we grew maize for 60 days under four watering regimes, (i) optimum (at field capacity) during 60 days, (ii) optimum from 0 to 30 days and stressed (50% field capacity) from 30 to 60 days, (iii) stressed from 0 to 30 days and optimum from 30 to 60 days, and (iv) stressed throughout the 60 days. Nitrogen was applied at three rates (none, moderate (45 kg N ha⁻¹) and high (120 kg N ha⁻¹)). Plants were sampled after 30 and 60 days. At 60 days, leaves developed during the first 30 days were sampled separately from those developed between 30 and 60 days. Shoot production showed a clear water–nitrogen interaction. Nitrogen response increased with decreasing water stress, in particular from 30 to 60 days. δ¹³C values ranged from −12.42‰ to −10.80‰. Overall, a clear and significant water and nitrogen effect (P<0.0001) on the isotopic discrimination in maize was observed, opposite in direction from C₃ plants. δ¹³C values decreased with increasing water stress, but increased with decreasing nitrogen availability, particularly when combined with limited water supply. In addition, isotopic discrimination was observed to be variable within plant, and could be related to a water stress in that growth period, in which the plant parts were developed. This shows that δ¹³C values measured in different plant parts at harvest can be used as a historical account on how water availability varied during the entire cropping cycle.     

Biometric Based Carbon Flux Measurements and Net Ecosystem Production (NEP) in a Temperate Deciduous Broad-Leaved Forest Beneath a Flux Tower

Biometric based carbon flux measurements were conducted over 5 years (1999–2003) in a temperate deciduous broad-leaved forest of the AsiaFlux network to estimate net ecosystem production (NEP). Biometric based NEP, as measured by the balance between net primary production (including NPP of canopy trees and of forest floor dwarf bamboo) and heterotrophic respiration (RH), clarified the contribution of various biological processes to the ecosystem carbon budget, and also showed where and how the forest is storing C. The mean NPP of the trees was 5.4 ± 1.07 t C ha⁻¹ y⁻¹, including biomass increment (0.3 ± 0.82 t C ha⁻¹ y⁻¹), tree mortality (1.0 ± 0.61 t C ha⁻¹ y⁻¹), aboveground detritus production (2.3 ± 0.39 t C ha⁻¹ y⁻¹) and belowground fine root production (1.8 ± 0.31 t C ha⁻¹ y⁻¹). Annual biomass increment was rather small because of high tree mortality during the 5 years. Total NPP at the site was 6.5 ± 1.07 t C ha⁻¹ y⁻¹, including the NPP of the forest floor community (1.1 ± 0.06 t C ha⁻¹ y⁻¹). The soil surface CO₂ efflux (RS) was averaged across the 5 years of record using open-flow chambers. The mean estimated annual RS amounted to 7.1 ± 0.44 t C ha⁻¹, and the decomposition of soil organic matter (SOM) was estimated at 3.9 ± 0.24 t C ha⁻¹. RH was estimated at 4.4 ± 0.32 t C ha⁻¹ y⁻¹, which included decomposition of coarse woody debris. Biometric NEP in the forest was estimated at 2.1 ± 1.15 t C ha⁻¹ y⁻¹, which agreed well with the eddy-covariance based net ecosystem exchange (NEE). The contribution of woody increment (Δbiomass + mortality) of the canopy trees to NEP was rather small, and thus the SOM pool played an important role in carbon storage in the temperate forest. These results suggested that the dense forest floor of dwarf bamboo might have a critical role in soil carbon sequestration in temperate East Asian deciduous forests.     

Competitive binding of Fe<Superscript>3+</Superscript>, Cr<Superscript>3+</Superscript>, and Ni<Superscript>2+</Superscript> to transferrin

Competitive binding of Fe³⁺, Cr³⁺, and Ni²⁺ to transferrin (Tf) was investigated at various physiological iron to Tf concentration ratios. Loading percentages for these metal ions are based on a two M ⁿ⁺ to one Tf (i.e., 100% loading) stoichiometry and were determined using a particle beam/hollow cathode–optical emission spectroscopy (PB/HC-OES) method. Serum iron concentrations typically found in normal, iron-deficient, iron-deficient from chronic disease, iron-deficient from inflammation, and iron-overload conditions were used to determine the effects of iron concentration on iron loading into Tf. The PB/HC-OES method allows the monitoring of metal ions in competition with Fe³⁺ for Tf binding. Iron-overload concentrations impeded the ability of chromium (15.0 μM) or nickel (10.3 μM) to load completely into Tf. Low Fe³⁺ uptake by Tf under iron-deficient or chronic disease iron concentrations limited Ni²⁺ loading into Tf. Competitive binding kinetic studies were performed with Fe³⁺, Cr³⁺, and Ni²⁺ to determine percentages of metal ion uptake into Tf as a function of time. The initial rates of Fe³⁺ loading increased in the presence of nickel or chromium, with maximal Fe³⁺ loading into Tf in all cases reaching approximately 24%. Addition of Cr³⁺ to 50% preloaded Fe³⁺–Tf showed that excess chromium (15.0 μM) displaced roughly 13% of Fe³⁺ from Tf, resulting in 7.6 ± 1.3% Cr³⁺ loading of Tf. The PB/HC-OES method provides the ability to monitor multiple metal ions competing for Tf binding and will help to understand metal competition for Tf binding.     

Invasion by a Perennial Herb Increases Decomposition Rate and Alters Nutrient Availability in Warm Temperate Lowland Forest Remnants

We determined the impact of the invasive herb, Tradescantia fluminensis Vell., on litter decomposition and nutrient availability in a remnant of New Zealand lowland podocarp–broadleaf forest. Using litter bags, we found that litter beneath mats of Tradescantia decomposed at almost twice the rate of litter placed outside the mat. Values of k (decomposition quotient) were 9.44±0.42 yrs for litter placed beneath Tradescantia and 5.42±0.42 yrs for litter placed in native, non-Tradescantia plots. The impact of Tradescantia on decomposition was evident through the smaller forest floor mass in Tradescantia plots (2.65±1.05 t ha⁻¹) compared with non-Tradescantia plots (5.05±1.05 t ha⁻¹), despite similar quantities of annual leaf litterfall into Tradescantia plots (6.85±0.85 t ha⁻¹ yr⁻¹) and non-Tradescantia plots (7.45±1.05 t ha⁻¹ yr⁻¹). Moreover, there was increased plant nitrate available, as captured on resin bags, in Tradescantia plots (25.77 ± 8.32 cmol(−)/kg resin) compared with non-Tradescantia plots (9.55±3.72 cmol(−)/kg resin). Finally, the annual nutrient uptake by Tradescantia represented a large proportion of nutrients in litterfall (41% N, 61% P, 23% Ca, 46% Mg and 83% K), exceeded the nutrient content of the forest floor (except Ca), but was a small proportion of the topsoil nutrient pools. Taken together, our results show that Tradescantia increases litter decomposition and alters nutrient availability, effects that could influence the long-term viability of the majority of podocarp–broadleaf forest remnants affected with Tradescantia in New Zealand. These impacts are likely mostly due to Tradescantia's vegetation structure (i.e., tall, dense mats) and associated microclimate, compared with native ground covers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pathways for K<Superscript>+</Superscript> Efflux in Isolated Surface and Crypt Colonic Cells. Activation by Calcium

K⁺-conductive pathways were evaluated in isolated surface and crypt colonic cells, by measuring ⁸⁶Rb efflux. In crypt cells, basal K⁺ efflux (rate constant: 0.24 ± 0.044 min⁻¹, span: 24 ± 1.3%) was inhibited by 30 mM TEA and 5 mM Ba²⁺ in an additive way, suggesting the existence of two different conductive pathways. Basal efflux was insensitive to apamin, iberiotoxin, charybdotoxin and clotrimazole. Ionomycin (5 μM) stimulated K⁺ efflux, increasing the rate constant to 0.65 ± 0.007 min⁻¹ and the span to 83 ± 3.2%. Ionomycin-induced K⁺ efflux was inhibited by clotrimazole (IC₅₀ of 25 ± 0.4 μM) and charybdotoxin (IC₅₀ of 65 ± 5.0 nM) and was insensitive to TEA, Ba²⁺, apamin and iberiotoxin, suggesting that this conductive pathway is related to the Ca²⁺-activated intermediate-conductance K⁺ channels (IK_ca). Absence of extracellular Ca²⁺ did neither affect basal nor ionomycin-induced K⁺ efflux. However, intracellular Ca²⁺ depletion totally inhibited the ionomycin-induced K⁺ efflux, indicating that the activation of these K⁺ channels mainly depends on intracellular calcium liberation. K⁺ efflux was stimulated by intracellular Ca²⁺ with an EC₅₀ of 1.1 ± 0.04 μM. In surface cells, K⁺ efflux (rate constant: 0.17 ± 0.027 min⁻¹; span: 25 ± 3.4%) was insensitive to TEA and Ba²⁺. However, ionomycin induced K⁺ efflux with characteristics identical to that observed in crypt cells. In conclusion, both surface and crypt cells present IK_Ca channels but only crypt cells have TEA- and Ba²⁺-sensitive conductive pathways, which would determine their participation in colonic K⁺ secretion.