Long-term hydrochemical monitoring in an Oyasan Experimental Forest Watershed comprised of two small forested watersheds of Japanese cedar and Japanese cypress

Forest ecosystems are self-fertilizing systems, and development of forest stands depends on nutrient supply via biogeochemical cycling within the ecosystem. Therefore, it is important to clarify the nutrient cycle mediating growth and development. In addition, long-term hydrochemical monitoring is needed to understand the influence of environmental changes on biogeochemical cycling in forest ecosystems. The Oyasan Experimental Forest Watershed (OEFW) is located in the Field Museum Oyasan, the university forest of Tokyo University of Agriculture and Technology, in Gunma prefecture, Japan. OEFW comprises two small adjacent forested watersheds—A-watershed and B-watershed—with respective areas of 1.3 and 1.8 ha. A-watershed is a reestablished forest planted with sugi (Japanese cedar; Cryptomeria japonica) and hinoki (Japanese cypress; Chamaecyparis obtusa) in 1976, and has been managed intensively with fertilizer application. By contrast, B-watershed is an established forest planted with sugi and hinoki in 1907. No forest practices have been carried out except for thinning of suppressed trees in 1983. However, the sugi plantation on the lowest slope (18% of the watershed area) was cut in 2000, and sugi was replanted the following year. In this data paper, we present data on the daily precipitation, discharge, pH, and concentrations of major nutrients (Ca²⁺, Mg²⁺, K⁺, Na⁺, NH₄ ⁺, Cl⁻, NO₃ ⁻, and SO₄ ²⁻) in rainwater and stream water since November 1978. The arithmetical mean pH of precipitation, stream water in A- and B-watershed from the beginning of the monitoring to the present were 4.77 ± 0.67, 6.85 ± 0.41 and 6.88 ± 0.36 (average ± SD), respectively. The arithmetical mean concentrations in precipitation in mmol_c L⁻¹ were 0.030 ± 0.030 for Ca²⁺, 0.010 ± 0.011 for Mg²⁺, 0.009 ± 0.013 for K⁺, 0.020 ± 0.024 for Na⁺, 0.035 ± 0.041 for NH₄ ⁺, 0.026 ± 0.029 for Cl⁻, 0.033 ± 0.038 for NO₃ ⁻, and 0.046 ± 0.043 for SO₄ ²⁻. The mean concentrations in stream water in A-watershed were 0.180 ± 0.032 for Ca²⁺, 0.073 ± 0.013 for Mg²⁺, 0.018 ± 0.009 for K⁺, 0.182 ± 0.024 for Na⁺, 0.010 ± 0.010 for NH₄ ⁺, 0.060 ± 0.008 for Cl⁻, 0.111 ± 0.038 for NO₃ ⁻, and 0.074 ± 0.012 for SO₄ ²⁻; whereas for B-watershed the mean concentrations were 0.169 ± 0.025 for Ca²⁺, 0.079 ± 0.016 for Mg²⁺, 0.018 ± 0.005 for K⁺, 0.192 ± 0.026 for Na⁺, 0.010 ± 0.010 for NH₄ ⁺, 0.065 ± 0.010 for Cl⁻, 0.093 ± 0.025 for NO₃ ⁻, and 0.087 ± 0.011 for SO₄ ²⁻.     

Hemoglobin senses body temperature

When aspirating human red blood cells (RBCs) into 1.3 μm pipettes (ΔP = −2.3 kPa), a transition from blocking the pipette below a critical temperature T _c = 36.3 ± 0.3°C to passing it above the T _c occurred (micropipette passage transition). With a 1.1 μm pipette no passage was seen which enabled RBC volume measurements also above T _c. With increasing temperature RBCs lost volume significantly faster below than above a T _c = 36.4 ± 0.7 (volume transition). Colloid osmotic pressure (COP) measurements of RBCs in autologous plasma (25°C ≤ T ≤ 39.5°C) showed a T _c at 37.1 ± 0.2°C above which the COP rapidly decreased (COP transition). In NMR T₁-relaxation time measurements, the T₁ of RBCs in autologous plasma changed from a linear (r = 0.99) increment below T _c = 37 ± 1°C at a rate of 0.023 s/K into zero slope above T _c (RBC T₁ transition). In conclusion: An amorphous hemoglobin–water gel formed in the spherical trail, the residual partial sphere of the aspirated RBC. At T _c, a sudden fluidization of the gel occurs. All changes mentioned above happen at a distinct T _c close to body temperature. The T _c is moved +0.8°C to higher temperatures when a D₂O buffer is used. We suggest a mechanism similar to a “glass transition” or a “colloidal phase transition”. At T _c, the stabilizing Hb bound water molecules reach a threshold number enabling a partial Hb unfolding. Thus, Hb senses body temperature which must be inscribed in the primary structure of hemoglobin and possibly other proteins. This article is dedicated to Ludwig Artmann who died on July 21, 2001 on a beautiful summer day during which we performed experiments far away. Ludwig Artmann was a man who encouraged us to be strong and to study hard no matter what were the costs.     

The cranial arterio-venous temperature difference is related to respiratory evaporative heat loss in a panting species,the sheep (<Emphasis Type="Italic">Ovis aries</Emphasis>)

Panting is a mechanism that increases respiratory evaporative heat loss (REHL) under heat load. Because REHL uses body water, it is physiologically and ecologically relevant to know under what conditions free-ranging animals use panting. We investigated whether the cranial arterio-venous temperature difference could provide information about REHL. We exposed sheep to environments varying in ambient dry bulb temperatures (Env 1: ~15°C, Env 2: ~25°C, Env 3: ~40°C, Env 4: ~40°C + infrared radiation) and measured REHL simultaneously with carotid arterial (T _car) and jugular venous (T _jug) blood temperatures, as well as brain (T _brain) and rectal (T _rec) temperatures. REHL increased significantly with ambient temperature, from 18.4 ± 4.5 W at Env 1 to 79.5 ± 12.6 W at Env 4 (P < 10⁻⁶). While there was no effect of environment on T _car (P = 0.7) or T _jug (P = 0.09), the difference between them (T _a-v = T _car − T _jug) increased from Env 1 to Env 2 (P = 0.04) and from Env 3 to Env 4 (P = 0.008). T _a-v reached a maximum of 0.7 ± 0.2°C at Env 4 and was positively correlated with REHL across environments (r ² = 0.78, F = 34.7, P < 10⁻³). Calculated cranial blood flow changed only from Env 2 to Env 3 (P = 0.002). The increase in REHL maintained homeothermy when dry heat loss decreased. While REHL could increase without generating an increase in T _a-v, any increase in T _a-v was always associated with an increase in REHL. We conclude that the cranial T _a-v provides useful information about REHL in panting animals.     

Glutathione and Vitamin B12 Cooperate in Stabilization of a B12 Trafficking Chaperone Protein

The protein bCblC (bCblCpro) is a bovine homolog of a human B₁₂ trafficking chaperone that is responsible for the processing of vitamin B₁₂ and its escorted delivery in intracellular B₁₂ metabolism. In this study, we found that bCblCpro is highly thermolabile with a T _m = 42.0 ± 0.2 °C as shown for the human homolog, suggesting thermal regulation of these proteins. Binding of the reduced form of glutathione (GSH) that is a predominant cellular thiol increased the T _m of bCblCpro from 42 °C to ~45 °C (ΔT _{m max} = 3.1 ± 0.2 °C and AC₅₀ = 2.1 ± 0.5 mM). Binding of vitamin B₁₂ and its derivatives also stabilized bCblCpro increasing the T _m to a different extent and vitamin B₁₂ (cyanocobalamin, CNCbl) was the least efficient (ΔT _{m max} = 4.3 ± 0.3 °C and AC₅₀ = 291 ± 36 μM). However, the stabilizing effect of CNCbl was significantly greater for GSH-bound bCblCpro (ΔT _{m max} = 12.8 ± 0.6 °C and AC₅₀ = 9.3 ± 1.6 μM) than for GSH-free bCblCpro. In addition, the stabilizing effect of GSH was also greater for CNCbl-bound bCblCpro (ΔT _{m max} = 9.3 ± 0.3 °C and AC₅₀ = 57.0 ± 6.8 μM). Limited proteolysis revealed that thermal stabilization of bCblCpro is derived from conformational changes of the protein induced by binding of the ligands. The results in this study indicate that GSH cooperates with vitamin B₁₂ in thermal stabilization of bCblCpro and is a positive regulator of the protein.     

Predicting tropical plant physiology from leaf and canopy spectroscopy

A broad regional understanding of tropical forest leaf photosynthesis has long been a goal for tropical forest ecologists, but it has remained elusive due to difficult canopy access and high species diversity. Here we develop an empirical model to predict sunlit, light-saturated, tropical leaf photosynthesis using leaf and simulated canopy spectra. To develop this model, we used partial least squares (PLS) analysis on three tropical forest datasets (159 species), two in Hawaii and one at the biosphere 2 laboratory (B2L). For each species, we measured light-saturated photosynthesis (A), light and CO₂ saturated photosynthesis (A _max), respiration (R), leaf transmittance and reflectance spectra (400–2,500 nm), leaf nitrogen, chlorophyll a and b, carotenoids, and leaf mass per area (LMA). The model best predicted A [r ²  = 0.74, root mean square error (RMSE) = 2.9 μmol m⁻² s⁻¹)] followed by R (r ²  = 0.48), and A _max (r ²  = 0.47). We combined leaf reflectance and transmittance with a canopy radiative transfer model to simulate top-of-canopy reflectance and found that canopy spectra are a better predictor of A (RMSE = 2.5 ± 0.07 μmol m⁻² s⁻¹) than are leaf spectra. The results indicate the potential for this technique to be used with high-fidelity imaging spectrometers to remotely sense tropical forest canopy photosynthesis.     

Edible oil degradation by using yeast coculture of <Emphasis Type="Italic">Rhodotorula pacifica</Emphasis> ST3411 and <Emphasis Type="Italic">Cryptococcus laurentii</Emphasis> ST3412

To develop a microbial treatment of edible oil-contaminated wastewater, microorganisms capable of rapidly degrading edible oil were screened. The screening study yielded a yeast coculture comprising Rhodotorula pacifica strain ST3411 and Cryptococcus laurentii strain ST3412. The coculture was able to degrade efficiently even at low contents of nitrogen ([NH₄–N] = 240 mg/L) and phosphorus sources ([PO₄–P] = 90 mg/L). The 24-h degradation rate of 3,000 ppm mixed oils (salad oil/lard/beef tallow, 1:1 w/w) at 20°C was 39.8% ± 9.9% (means ± standard deviations of eight replicates). The highest degradation rate was observed at 20°C and pH 8. In a scaled-up experiment, the salad oil was rapidly degraded by the coculture from 671 ± 52.0 to 143 ± 96.7 ppm in 24 h, and the degradation rate was 79.4% ± 13.8% (means ± standard deviations of three replicates). In addition, a repetitive degradation was observed with the cell growth by only pH adjustment without addition of the cells.     

Winter body temperature patterns in free-ranging Cape ground squirrel, Xerus inauris: no evidence for torpor

The body temperature (T _b) of Cape ground squirrels (Xerus inauris, Sciuridae) living in their natural environment during winter has not yet been investigated. In this study we measured abdominal T _b of eight free-ranging Cape ground squirrels over 27 consecutive days during the austral winter. Mean daily T _b was relatively stable at 37.0 ± 0.2°C (range 33.4 to 40.2°C) despite a marked variation in globe temperature (T _g) (range −7 to 37°C). Lactating females (n = 2) consistently had a significantly higher mean T _b (0.7°C) than non-lactating females (n = 3) and males. There was a pronounced nychthemeral rhythm with a mean active phase T _b of 38.1 ± 0.1°C and a mean inactive phase T _b of 36.3 ± 0.3°C for non-lactating individuals. Mean daily amplitude of T _b rhythm was 3.8 ± 0.2°C. T _b during the active phase closely followed T _g and mean active phase T _b was significantly correlated with mean active phase T _g (r ² = 0.3–0.9; P < 0.01). There was no evidence for daily torpor or pronounced hypothermia during the inactive phase, and mean minimum inactive phase T _b was 35.7 ± 0.3°C for non-lactating individuals. Several alternatives (including nocturnal huddling, an aseasonal breeding pattern and abundant winter food resources) as to why Cape ground squirrels do not employ nocturnal hypothermia are discussed.     

Analysis of stream water temperature changes during rainfall events in forested watersheds

Despite continued interest in stream water temperature (Tw) analysis, there are few studies of Tw response to rainfall events at forested watersheds. We examined 61 sets of data on Tw for 21 rainfall events at 16 watersheds with various slope gradients (from 0.08 to 0.56) in four regions of Japan from June 2004 to December 2005. The investigation focused on the changes of specific discharge (ΔQs) and ΔTw at medium-sized watersheds (0.5–100 ha). The results clearly demonstrated different flow patterns expressed by Qs vs. Tw hysteretic loops. Those were clockwise in Period I (April–September) and counterclockwise in Period II (October–March), except for lower slope gradient at Aichi, where counterclockwise loops were observed in both periods. These differences in hysteretic loops could be explained by the differences in Tw and in response times to rainfall between surface/subsurface and groundwater flows. The response times were probably determined by the slope gradient and the vertical level of groundwater. We also found that the changes in air temperature (ΔTa) influenced ΔTw to a lesser degree than Qs. The average rainfall intensities in Period I and Period II (9.3 ± 1.7 and 5.4 ± 0.2 mm/h, respectively) affected the average values of ΔQs and ΔTw (6.62 ± 4.08 mm/h and 1.7 ± 0.4°C; 0.85 ± 0.68 mm/h and 0.9 ± 0.3°C, respectively). This indicates that slope gradient and Qs influenced ΔTw by changing the relative proportions of flow paths. In addition, the water table changes influenced the percentage of groundwater flow to the stream.     

Development,Optimization, and Anti-diabetic Activity of Gliclazide-Loaded Alginate–Methyl Cellulose Mucoadhesive Microcapsules

The purpose of this work was to develop and optimize gliclazide-loaded alginate–methyl cellulose mucoadhesive microcapsules by ionotropic gelation using central composite design. The effect of formulation parameters like polymer blend ratio and cross-linker (CaCl₂) concentration on properties of gliclazide-loaded alginate–methyl cellulose microcapsules like drug encapsulation efficiency and drug release were optimized. The optimized microcapsules were subjected to swelling, mucoadhesive, and in vivo studies. The observed responses coincided well with the predicted values from the optimization technique. The optimized microcapsules showed high drug encapsulation efficiency (83.57 ± 2.59% to 85.52 ± 3.07%) with low T _50% (time for 50% drug release, 5.68 ± 0.09 to 5.83 ± 0.11 h). The in vitro drug release pattern from optimized microcapsules was found to be controlled-release pattern (zero order) with case II transport release mechanism. Particle sizes of these optimized microcapsules were 0.767 ± 0.085 to 0.937 ± 0.086 mm. These microcapsules also exhibited good mucoadhesive properties. The in vivo studies on alloxan-induced diabetic rats indicated the significant hypoglycemic effect that was observed 12 h after oral administration of optimized mucoadhesive microcapsules. The developed and optimized alginate–methyl cellulose microcapsules are suitable for prolonged systemic absorption of gliclazide to maintain lower blood glucose level and improved patient compliance.     

Is the response of coral calcification to seawater acidification related to nutrient loading?

The effect of decreasing aragonite saturation state (Ω_Arag) of seawater (elevated pCO₂) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Réunion Island, western Indian Ocean): a back-reef site (BR) affected by nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO₂ (1,440–340 μatm), Ω_Arag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg⁻¹). Increasing DIC concentrations at constant total alkalinity (A_T) resulted in a decrease in Ω_Arag and an increase in pCO₂. A_T at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg⁻¹ (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and A_T during the incubations. Calcification decrease in response to doubling pCO₂ relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO₂ treatments at BR compared to low pCO₂ treatments, and (3) calcification was not related to Ω_Arag at BR. When normalized to NP, calcification was linearly related to Ω_Arag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO₂ treatments may have increased calcification and thus masked the negative effect of low Ω_Arag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased Ω_Arag (increased pCO₂) whatever the nutrient loading.     

Intranasal Microemulsion of Sildenafil Citrate: In Vitro Evaluation and In Vivo Pharmacokinetic Study in Rabbits

The purpose of the present study was to prepare intranasal delivery system of sildenafil citrate and estimate its relative bioavailability after nasal administration in rabbits to attain rapid onset of action with good efficacy at lower doses. Sildenafil citrate saturated solubility was determined in different solvents, cosolvents, and microemulsion systems. For nasal application, sildenafil citrate was formulated in two different systems: the first was a cosolvent system (S3) of benzyl alcohol/ethanol/water/Transcutol/taurodeoxy cholate/Tween 20 (0.5:16.8:47.7:15.9:1:18.1% w/w). The second was a microemulsion system (ME6) containing Oleic acid: Labrasol/Transcutol/water (8.33:33.3:16.66:41.66% w/w). The prepared systems were characterized in relation to their clarity, particle size, viscosity, pH, and nasal ciliotoxicity. In vivo pharmacokinetic performance of the selected system ME6 (with no nasal ciliotoxicity) was evaluated in a group of six rabbits in a randomized crossover study and compared to the marketed oral tablets. The targeted solubility (>20 mg/ml) of sildenafil citrate was achieved with cosolvent systems S1, S3, and S5 and with microemulsion systems ME3–ME6. The saturated solubility of sildenafil citrate in cosolvent system S3 and microemulsion system ME6 were 22.98 ± 1.26 and 23.79 ± 1.16 mg/ml, respectively. Microemulsion formulation ME6 showed shorter t _max (0.75 h) and higher AUC_(0-∞) (1,412.42 ng h/ml) compared to the oral tablets which showed t _max equals 1.25 h and AUC_(0-∞) of 1,251.14 ng h/ml after administration to rabbits at dose level of 5 mg/kg. The relative bioavailability was 112.89%. In conclusion, the nasal absorption of sildenafil citrate microemulsion was found to be fast, indicating the potential of nasal delivery instead of the conventional oral administration of such drug.     

Cost-benefit relationships in sclerophyllous leaves of the ‘Bana’ vegetation in the Amazon region

This study estimated the construction const (CC) and maintenance cost (MC) of leaf tissue on the basis of dry mass (CC_Mass, MC_Mass) and leaf area (CC_Area, MC_Area), as well as the maximum leaf gas exchange capacity, so as to examine leaf cost:benefit relationship in six dominant species of the ‘Bana’ vegetation. Minimum and maximum CC_Mass averaged 1.71 ± 0.03 and 1.78 ± 0.03 g glucose g⁻¹. The CC_Mass showed a statistically significant positive correlation with crude fibre, and tended to decline as leaves were larger. Thus, smaller leaves tended to be built out of a more expensive material than that found in species bearing larger leaves. The average CC_Area of the ‘Bana’ species was 376 ± 15 g glucose m⁻². A robust correlation was found between CC_Area with leaf dry mass to leaf area ratio, as well as with leaf thickness, but not with leaf density. MC_Mass (g glucose g⁻¹ day⁻¹) and MC_Area (g glucose m⁻² day⁻¹⁾ were positively correlated. Maximum and minimum MC_Mass increased significantly with protein and lipid content, respectively. Maximum carbon assimilation (A _max) was positively correlated with CC_Area. All the species operated at high stomatal conductance (g _s) and C _i/C _a which suggested low short-term water use efficiency. Potential nitrogen use efficiency (PNUE = A _max/N) averaged 35.4 ± 1.8 mmol CO₂ mol⁻¹ N. As the sclerophylly index (g crude fibre g⁻¹ protein) increased, the ratio of CC_Area to A _max increased significantly. This result suggests a trade-off between investments in an expensive resistant sclerophyllous leaf which should maximize carbon gain in the long term.     

Home range,range overlap,and site fidelity of introduced Siberian chipmunks in a suburban French forest

Home range size, range overlap, and multiyear site fidelity were investigated for introduced Siberian chipmunks (Tamias sibiricus) in a French suburban forest from bimonthly trapping sessions for 4 years (2004–2007). Annual home range sizes (100% minimum convex polygon, ±SE) were estimated from 39 trapping histories of 28 different adult residents. Males (N = 13, 1.86 ± 0.32 ha) had a home range 2.5 times larger than females (N = 26, 0.71 ± 0.08 ha); a male home range included significantly more trapping centers (arithmetic mean of capture locations) of females (5.5 ± 0.7) than of males (2.3 ± 0.5). Chipmunks exhibited strong multiyear site fidelity: mean distance between annual trapping centers of individuals trapped over two successive years was small (N = 82, 26 ± 2 m) compared to the largest home range length (ranging from 36 to 281 m); overlap between annual home range sizes of residents was 84 ± 5% (N = 11). These results improve our understanding of the space occupation of this unknown species in a novel environment.     

Quercetin in Lyotropic Liquid Crystalline Formulations: Physical, Chemical and Functional Stability

The purpose of this study was to develop a lyotropic liquid crystalline formulation using the emulsifier vitamin E TPGS and evaluate its behavior after incorporation of a flavonoid, quercetin. The physical (macro and microscopic), chemical (determination of quercetin content by the HPLC method) and functional (determination of quercetin antioxidant activity by DPPH^• assay) stability of the lamellar liquid crystalline formulation containing flavonoid was evaluated when stored at 4 ± 2 °C; 30 ± 2 °C/70 ± 5% RH (relative humidity) and 40 ± 2 °C/70 ± 5% RH during 12 months. The lamellar liquid crystalline structure of the formulation was maintained during the experiment, however chemical and functional stability results showed a great influence of the storage period in all conditions tested. A significant decrease in quercetin content (approximately 40%) was detected during the first month of storage and a similar significant loss in antioxidant activity was detected after 6 months. The remaining flavonoid content was unchanged during the final 6 months of the experimental period. The results suggest possible interactions between quercetin and the liquid crystalline formulation, which could inhibit or reduce the quercetin activity incorporated in the system. In conclusion, the present study demonstrated that incorporation of quercetin (1%) did not affect the liquid crystalline structure composed of vitamin E TPGS/IPM/PG–H₂O (1:1) at 63.75/21.25/15 (w/w/w). Nevertheless, of the total quercetin incorporated in the system only 60% was free to act as an antioxidant.     

Is distribution of hydraulic constraints within tree crowns reflected in photosynthetic water-use efficiency? An example of <Emphasis Type="Italic">Betula pendula</Emphasis>

Spatial and daily variation in photosynthetic water-use efficiency was examined in leaves of Betula pendula Roth with respect to distribution of hydraulic conductance within the crown, morphological properties of stomata, and water availability. Intrinsic water-use efficiency (A _n/g _s) was determined from gas-exchange measurements performed both in situ in a natural forest stand and on detached shoots under laboratory conditions. In intact foliage, sun leaves demonstrated significantly higher (P < 0.001) A _n/g _s than shade leaves, as photosynthesis in the lower canopy was chronically limited by low light availability. However, this difference reversed in the mid-day period under sufficient irradiance (I > 800 μmol m⁻² s⁻¹): A _n/g _s averaged 28.8 and 24.0 μmol mol⁻¹ (P < 0.01) for shade and sun leaves, respectively. This last finding coincided with the data obtained in laboratory conditions: under equivalent leaf water supply and light, A _n/g _s in shade foliage was greater (P < 0.001) than in sun foliage across a wide range of irradiance. Thus, shade foliage of B. pendula is characterized by inherently higher A _n/g _s than sun foliage, associated with more conservative stomatal behavior, and lower soil-to-leaf (K _T) and leaf hydraulic conductances. Under unlimited light conditions, a within-crown trade-off between A _n/g _s and K _T becomes apparent. Differences in stomatal conductance between the detached shoots from sunlit and shaded canopy layers were largely attributable to the variation in stomatal morphology; significant relationships were established with characteristics combining stomatal size and density (relative stomatal surface, stomatal pore area index). Stomatal morphology is very likely involved in long-term adjustment of photosynthetic WUE.     

Water relations and gas exchange in Fagus sylvatica L. and Quercus petraea (Mattuschka) Liebl. in a mixed stand at their southern limit of distribution in Europe

Water status and gas exchange of beech (Fagus sylvatica L.) and sessile oak [Quercus petraea (Mattuschka) Liebl.] were studied in a mixed stand in the Montejo de la Sierra forest (central Iberian Peninsula), one of the southernmost locations of both species in Europe. Gas exchange and water potential were measured in leaves at different canopy levels over several days in two growing seasons. The daily variation pattern was established with the measurements of three selected dates per year, representative of the soil moisture content situations in early, mid- and late summer. A similar daily time course of leaf water potential was found for the two species. Nevertheless, beech showed a most noticeable decrease of water potential at midmorning and maintained lower leaf water potential than oak in the early afternoon. In 1994 the sessile oak saplings showed higher values of predawn water potential (Ψ_pd) than beech at the end of summer, when soil moisture content was lowest (20 cm depth). Beech showed a significantly lower net assimilation rate (A) than sessile oak for leaves under the same PPFD. Maximum net photosynthesis values (A _max) for beech and sessile oak on sunny leaves were 10.1±0.4 μmol m^–2 s^–1 and 17.8±1.7 μmol m^–2 s^–1 respectively, and those for water vapour stomatal conductance (g _wv) were 265±31 mmol m^–2 s^–1 and 438±74 mmol m^–2 s^–1. Differences in A and g _wv between the two species were maintained throughout the day on all measurement dates. No clear relationship was found between water status of saplings and stomata performance; there was only a negative correlation between Ψ_pd and g _wvmid in beech. Nevertheless, a significant response to the air vapour pressure gradient between leaf and air was translated into stomata closure on an hourly basis, more intensively in beech. Received: 4 March 1999 / Accepted: 21 December 1999     

Purification and Characterisation of Rat Kidney Glutathione Reductase

Glutathione reductase [GR, E.C.1.8.1.7] catalyses NADPH dependent reduction of glutathione disulfide (GSSG) to reduced glutathione (GSH). Thus, it is the crucial enzyme to maintain high [GSH]/[GSSG] ratio and physiological redox status in cells. Kidney and liver tissues were considered as a rich source of GR. In this study, rat kidney GR was purified and some of its properties were investigated. The enzyme was purified 2,356 fold with a yield of 16% by using heat-denaturation and Sephadex G25 gel filtration, 2′,5′-ADP Agarose 4B, PBE94 column chromatographies. The purified enzyme had a specific activity (Vm) of 250 U/mg protein and the ratio of absorbances at wavelengths of A ₂₇₃/A _463, A ₂₈₀/A ₄₆₀, A ₃₆₅/A ₄₆₀, and A ₃₇₉/A ₄₆₃, were 7.1, 6.8, 1.2 and 1.0, respectively. Each mol of GR subunit bound 0.97 mol of FAD. NADH was used as a coenzyme by rat kidney GR but with a lower efficiency (32.7%) than NADPH. Its subunit molecular weight was estimated as 53 kDa. An optimum pH of 6.5 and optimum temperature of 65 °C were found for rat kidney GR. Its activation energy (Ea) and temperature coefficient (Q₁₀) were calculated as 7.02 kcal/mol and 1.42, respectively. The Km_(NADPH) and kcat/Km _(NADPH) values were found to be 15.3 ± 1.4 μM and 1.68 × 10⁷ M⁻¹ s⁻¹ for the concentration range of 10-200 μM NADPH and when GSSG is the variable substrate, the Km_(GSSG) and the kcat/Km_(GSSG) values of 53.1 ± 3.4 μM and 4.85 × 10⁶ M⁻¹ s⁻¹ were calculated for the concentration range of 20–1,200 μM GSSG.     

Use of soybean vinasses as a germinant medium for a Geobacillus stearothermophilus ATCC 7953 sterilization biological indicator

A novel low-cost medium was developed from by-products and wastes from the ethanol agro-industry to replace commercial media in the production of a steam sterilization biological indicator (BI). Various recovery media were developed using soybean or sugarcane molasses and vinasse to prepare a self-contained BI. Media performance was evaluated by viability and heat resistance (D _121 °C value) according to regulatory standards. A medium produced with a soybean vinasse ratio of 1:70 (1.4%) (w/v) produced the results, with D _121 °C = 2.9 ± 0.5 min and Usk = 12.7 ± 2.1 min. The addition of 0.8% (w/v) yeast extract improved the germination of heat-damaged spores. The pH variation from 6.0 to 7.3 resulted in a gradual increase in the D _121 °C value. The absence of calcium chloride resulted in a decrease in germination, while no significant differences were observed with starch addition. Soybean vinasses may thus be used as the main component of a culture medium to substitute for commercial media in the production of self-contained biological indicators. The use of ethanol production waste in this biotechnological process realized a reliable performance, minimized the environmental impact, and decreased BI production costs while producing a high quality product.     

Electrophysiologic Characteristics of the Crista Terminalis and Implications on Atrial Tachycardia in Rabbits

The objective of this study was to evaluate the electrophysiologic characteristics of Crista terminalis (CT) and their implication in the pathogenesis of atrial tachycardia in rabbits. For this purpose, 27 New Zealand rabbits were used. Using standard glass microelectrode technique, cellular action potentials (APs) of CT and pectinate muscle (PM) were recorded in normal Tyrode’s perfusion and Tyrode’s perfusion with 4 μM isoproterenol. Longitudinal conduction velocity (V _L) and transverse conduction velocity (V _T) of CT were measured. As our data show, CT tissue had a trend of spontaneous phase IV depolarization. Conduction anisotropy (V _L/V _T) of CT was 4.53 ± 0.91. The duration of the AP of CT was longer than that of PM cells. APD₂₀ and APD₉₀ for CT were 28.1 ± 3.5 and 145.3 ± 7.1 ms; and for PM cells were 21.8 ± 4.1 and 125.3 ± 6.3 ms, respectively (all P values < 0.01). The early and delayed action depolarizations were recorded after isoproterenol perfusion. A fast paroxysmal irregular rhythm was recorded which could be arrested by 0.1 mmol/l Isoptin. It was, therefore, concluded that the latent autorhythmicity, trigger activity, and conduction properties of CT might provide the electrophysiologic basis for the occurrence and sustenance of atrial arrhythmia.