Mild Environmental Conditions Research Articles

Immobilization of trypsin in the layer-by-layer coating of graphene oxide and chitosan on in-channel glass fiber for microfluidic proteolysis

In this report, trypsin was immobilized in the layer-by-layer (LBL) coating of graphene oxide (GO) and chitosan on a piece of glass fiber to fabricate microchip bioreactor for efficient proteolysis. LBL deposition driven by electrostatic forces easily took place on the surface of the glass fiber, providing mild environmental conditions so that the denaturation and autolysis of the immobilized trypsin was minimized. Prior to use, a piece of the prepared trypsin-immobilized glass fiber was inserted into the channel of a microchip to form a core-changeable bioreactor. The novel GO-based bioreactor can be regenerated by changing its fiber core. The feasibility and performance of the unique bioreactor were demonstrated by the tryptic digestion of bovine serum albumin, myoglobin, cytochrome c, and hemoglobin and the digestion time was significantly reduced to less than 10 s. The obtained digests were identified by MALDI-TOF MS. The digestion performance of the core-changeable GO-based microchip bioreactor was comparable to that of 12-h in-solution tryptic digestion. The novel microchip bioreactor is simple and efficient, offering great promise for high-throughput protein identification.

Responsive microcapsule reactors based on hydrogen-bonded tannic acid layer-by-layer assemblies

We explore responsive properties of hollow multilayer shells of tannic acid assembled with a range of neutral polymers, poly(N-vinylpyrrolidone) (PVPON), poly(N-vinylcaprolactam) (PVCL) or poly(N-isopropylacrylamide) (PNIPAM). We found that properties of the nanoscale shells fabricated through hydrogen-bonded layer-by-layer (LbL) assembly can be tuned changing the interaction strength of a neutral polymer with tannic acid, and by a change in counterpart hydrophobicity. Unlike most hydrogen-bonded LbL films with two polymer components, the produced tannic acid-based multilayer shells are extremely stable in the wide pH range from 2 to 10. We demonstrate that gold nanoparticles can be grown within tannic acid-containing shell walls under mild environmental conditions paving the way for further modification of the capsule walls through thiol-based surface chemistry. Moreover, these shells show reversible pH-triggered changes in surface charge and permeability towards FITC-labeled polysaccharide molecules. The permeability of these LbL containers can be controlled by changing pH providing an opportunity for loading and release of a functional cargo under mild conditions.

183 EXERCISE INFLUENCES EMBRYO QUALITY IN MARES

Athletic mares are commonly utilized in an embryo transfer regimen during the breeding season, which allows owners to continue to train and compete with these animals. Exercising mares in a hot and humid environment has proven detrimental to embryo recovery rates. However, the effects of exercise under milder temperatures have not been examined. Our goal was to compare embryo recovery rates and embryo quality scores of mares under mild environmental conditions of 2 differing exercise regimens v. a single control group (n = 5). One treatment group (full exercise) consisted of mares (n = 5) exercised 6 days a week throughout the duration of the project. The partial-exercise group (n = 5) was exercised throughout the duration of the project 7 days a week, with full rest from day of detected ovulation to the proceeding embryo collection attempt. This was to limit any deleterious effects exercise may potentially have on the mare and subsequent early developing equine embryo. Exercise resumed the day after an embryo collection attempt for the partial-exercise group. Exercised mares were given a 1-month training period prior to the beginning of this project and were moderately exercised for 30 min in a mechanical exercise pen (free exerciser). Control mares were managed similarly as the other groups, however were not exercised. Mares were bred via artificial insemination and embryos were nonsurgically collected 7 d post-ovulation. Mean environmental temperature during the duration of this study was 27.1°C with average 60% humidity. Immediately following completion of exercise, mares in the full exercise group had a mean temperature increase of 1.0°C and partial-exercised mares increased 0.9°C. Exercise had a significant effect on embryo quality (P < 0.05, Table 1) but did not influence embryo recovery rate. The mean embryo quality score for the control group was 1.1, whereas the full-exercised group was 1.85 and partial-exercised group was 2.5. It appears from these data that exercise has a negative effect on embryo quality, thus lowering the availability of transferable embryos. Embryos of lower quality (≥3) have been shown to result in poor pregnancy rates in horses. Additionally, rest from ovulation to an embryo collection attempt did not improve embryo quality. Table 1.Embryo recovery rate and quality score of embryos from control and exercised mares

Urease Activity and Urea Gene Sequencing of Coccoid Forms of H. pylori Induced by Different Factors

Helicobacter pylori exists in two morphologic forms: spiral shaped and coccoid. The nonculturable coccoid forms were believed to be the morphologic manifestations of cell death for a long time. However, recent studies indicate the viability of such forms. This form of H. pylori is now suspected to play a role in the transmission of the bacteria and is partly responsible for relapse of infection after antimicrobial treatment. Urease activity of H. pylori is an important maintenance factor. Determination of urease activity and possible mutations in the DNA sequences of coccoid bacteria will hence contribute to the understanding of pathogenesis of infections, which these forms might be responsible for. In this study, our aim was to analyze the urease activity and investigate the urease gene sequences of coccoid H. pylori forms induced by different factors with respect to the spiral form. For this purpose, the urease activities of H. pylori NCTC 11637 standard strain and two clinical isolates were examined before and after transformation of the cells to coccoid forms by different methods such as exposure to amoxicillin, aerobiosis, cold starvation, and aging. The effects of these conditions on the urease gene were examined by the amplification of 411-bp ureA gene and 115-bp ureB gene regions by PCR technique and sequencing of the ureA gene. The urease activities of coccoid cells were found to be lower than those of the spiral form. ureA and ureB gene regions were amplified in all coccoid cells by PCR. Inducing the change to coccoid form by different methods was found to have no effect on the nucleotide sequence of the ureA gene. These results show that the urease gene region of coccoid H. pylori is highly protected under various mild environmental conditions.

Effects of wildfire, salvage logging and slash manipulation on Pinus pinaster Ait. recruitment in Orense (NW Spain)

Abstract The effect of wildfire and the subsequent harvesting on P. pinaster recruitment was evaluated in a burned stand of this species in Orense (Galicia, NW Spain). Most of the seedling emergence (88%) that occurred during the first year after wildfire, took place between the end of the winter and the beginning of the spring, although meteorological conditions during the first autumn after fire were not adverse. The mild environmental conditions during the first summer after wildfire resulted in very low seedling mortality. The degree of crown damage caused by wildfire significantly and negatively affected pine seedling stocking, which was, as average, 3.5 seedlings m −2 at the end of the first year after wildfire. Salvage logging was carried out 13 months after the fire. Three post-fire alternatives were compared: no harvesting (standing burned trees), harvesting + windrowing slash and harvesting + slash chopping. Slash chopping favoured a new seedling cohort. Harvesting and slash windrowing caused an immediate seedling mortality of 22%. Harvesting and slash chopping operations caused a mean mortality of 18 and 31%, respectively. Averaged over both slash treatments, 27% of the seedlings were damaged, which increased deferred mortality during the subsequent months. Pine seedling survival was significantly related to seedling height, especially in harvested plots and was significantly reduced by harvesting and logging slash operations, with this reduction significantly higher in the harvest + slash chopping treatment. Harvesting and slash manipulation significantly reduced seedling height and growth, especially after slash chopping. The percentage of bare soil resulting from clearcutting was significantly and negatively related to P. pinaster density, survival and height. Because of the contribution of the new cohort, at the end of the study there were no differences in seedling density related to treatment; the densities ranged from 3.4 seedlings m −2 in the non-harvested treatment to 2.5 seedlings m −2 in harvest + slash windrowing treatment, whereas in the harvest + slash chopping treatment these were 3.2 seedlings m −2 . The delay in harvesting may have lessened the impact of these forestry operations on P. pinaster recruitment. Reduction in seedling density caused by harvest and slash manipulation operations might reduce the need for subsequent thinning operations.

Environmental effects on poly‐p‐phenylenebenzobisoxazole fibers. I. Mechanisms of degradation

AbstractThis is the first of a two‐part series investigating the degradation mechanisms of PBO fiber and approaches to alleviating degradation and improving fiber properties. Poly‐p‐phenylenebenzobisoxazole (PBO) fiber is a high strength and modulus fiber with remarkable thermal stability. Recent in‐service failures of this fiber have revealed that the fiber degrades rapidly in relatively mild environmental conditions of moisture and heat. In this work the mechanisms of degradation due to moisture, the presence of acid, and the effect of radiation from the UV–vis spectrum are investigated. It is found that exposure to moisture results in the loosening of the fiber morphology leading to an increase in the number and size of defects. The presence of aqueous acid causes both loosening of the fiber structure and hydrolysis of the oxazole ring structure. The effect of UV–vis radiation is primarily hydrolysis of the material near the fiber surface with attendant formation of amide linkages. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3517–3525, 2006

Isolation and characterization of halophilic archaea able to grow in aromatic compounds

Benzoic acid and its hydroxylated derivatives are naturally occurring compounds that are also released into the environment in large amounts through industrial wastewater, automobile exhaust and tobacco smoke. Even though these compounds are readily degraded under mild environmental conditions, little is known about their metabolism in extreme environments such as hypersaline lakes. Five hypersaline sites, the Uyuni Salar (Bolivia), solar salterns in Cahuil (Chile), solar salterns in Cabo Rojo (Puerto Rico), sabkhas (Saudi Arabia) and the Dead Sea (Jordan), were tested for the presence of halophilic archaea able to metabolize aromatic compounds:. Forty-four new halophilic archaea able to grow in p-hydroxybenzoic acid (0.4 mM) as the sole carbon and energy source were isolated. On the basis of the metabolic and genetic diversity of these isolates, and their occurrence in all tested sites, it is suggested the ability to degrade p-hydroxybenzoic acid is a widespread feature among the Halobacteriaceae.

Autonomous artificial nanomotor powered by sunlight

Light excitation powers the reversible shuttling movement of the ring component of a rotaxane between two stations located at a 1.3-nm distance on its dumbbell-shaped component. The photoinduced shuttling movement, which occurs in solution, is based on a "four-stroke" synchronized sequence of electronic and nuclear processes. At room temperature the deactivation time of the high-energy charge-transfer state obtained by light excitation is approximately 10 micros, and the time period required for the ring-displacement process is on the order of 100 micros. The rotaxane behaves as an autonomous linear motor and operates with a quantum efficiency up to approximately 12%. The investigated system is a unique example of an artificial linear nanomotor because it gathers together the following features: (i) it is powered by visible light (e.g., sunlight); (ii) it exhibits autonomous behavior, like motor proteins; (iii) it does not generate waste products; (iv) its operation can rely only on intramolecular processes, allowing in principle operation at the single-molecule level; (v) it can be driven at a frequency of 1 kHz; (vi) it works in mild environmental conditions (i.e., fluid solution at ambient temperature); and (vii) it is stable for at least 10(3) cycles.

Effect of Carbohydrate Intake on Half-Marathon Performance of Well-Trained Runners

Eighteen highly-trained runners ran two half marathons in mild environmental conditions, 3 wk apart, consuming either 426 +/- 227 mL of a flavored placebo drink (PLACEBO) or an equivalent volume of water (386 +/- 185 mL) and a commercial gel (GEL) supplying 1.1 +/- 0.2 g/kg body mass (BM) carbohydrate (CHO). Voluntary consumption of this fluid was associated with a mean BM change of approximately 2.4%. Runners performed better in their second race by 0.9% or 40 s (P = 0.03). Three runners complained of gastrointestinal discomfort in GEL trial, which produced a clear impairment of half-marathon performance by 2.4% or 105 s (P=0.03). The effect of GEL on performance was trivial: time was improvedby 0.3% or 14 s compared with PLACEBO (P = 0.52). Consuming the gel was associated with a 2.4% slower time through the 2 x 200 m feed zone; adding a trivial approximately 2 s to race time. Although benefits to half marathon performance were not detected, the theoretical improvement during 1-h exercise with CHO intake merits further investigation.

Environmental sensitivity of gas exchange in different-sized trees

The carbon isotope signature (delta13C) of foliar cellulose from sunlit tops of trees typically becomes enriched as trees of the same species in similar environments grow taller, indicative of size-related changes in leaf gas exchange. However, direct measurements of gas exchange in common environmental conditions do not always reveal size-related differences, even when there is a distinct size-related trend in delta13C of the very foliage used for the gas exchange measurements. Since delta13C of foliage predominately reflects gas exchange during spring when carbon is incorporated into leaf cellulose, this implies that gas exchange differences in different-sized trees are most likely to occur in favorable environmental conditions during spring. If gas exchange differs with tree size during wet but not dry conditions, then this further implies that environmental sensitivity of leaf gas exchange varies as a function of tree size. These implications are consistent with theoretical relationships among height, hydraulic conductance and gas exchange. We investigated the environmental sensitivity of gas exchange in different-sized Douglas-fir (Pseudotsuga menziesii) via a detailed process model that specifically incorporates size-related hydraulic conductance [soil-plant-atmosphere (SPA)], and empirical measurements from both wet and dry periods. SPA predicted, and the empirical measurements verified, that differences in gas exchange associated with tree size are greatest in wet and mild environmental conditions and minimal during drought. The results support the hypothesis that annual net carbon assimilation and transpiration of trees are limited by hydraulic capacity as tree size increases, even though at particular points in time there may be no difference in gas exchange between different-sized trees. Maximum net ecosystem exchange occurs in spring in Pacific Northwest forests; therefore, the presence of hydraulic limitations during this period may play a large role in carbon uptake differences with stand-age. The results also imply that the impacts of climate change on the growth and physiology of forest trees will vary depending on the age and size of the forest.

Recent Advances in the Industrial Enzymatic Synthesis of Semi-Synthetic βLactam Antibiotics

The production, under environmentally benign conditions, of efficient and more cost-effective anti-infective agents (available to the whole mankind) is one of most ambitious dreams of the industrial medicinal chemistry. Semi-synthetic βlactam antibiotics are very effective anti-infective agents. They are very stable and can be used via oral delivery. They exhibit a very wide spectrum of anti-bacterial activity and minimal side effects after being massively used for a very long time. In this way, we can assume that semi-synthetic β-lactam antibiotics are going to be one of the key anti-infective agents in the next years. The condensation of natural or modified antibiotic nuclei with different acyl donor chains is one of the key steps for the industrial synthesis of these anti-infective agents. Up to now, these condensations are mainly carried out through classical chemical methods and this implies a number of economical, ecological and technological drawbacks (high energy requirements, many protection and deprotection steps, utilization of toxic methylene chloride as solvent, etc). Enzyme biocatalysts may be very useful to catalyse these selective condensations under very mild experimental and environmental conditions. In fact, the possibility of using enzymes to carry out such biotransformations, at laboratory scale, has been discussed and demonstrated a long time ago. However, industrial synthesis of βlactamic antibiotics is still carried out via unfavorable chemical routes. In fact, enzymes have not been produced in the nature to act in industrial reactors; so they are usually very unstable, inhibited by substrates and products and they may not have ideal catalytic properties for industrial uses (high reaction rates, required selectivity, ability to reach quantitative synthetic yields, stable enough to run a number of reaction cycles, etc). These limitations of enzyme biocatalysis become even more significant mainly when the enzyme is going to be used with non-natural substrates, catalysing non-natural processes and working under non-conventional conditions. However, in the last ten years, a great number of papers have reported substantial improvement of these enzymatic synthetic approaches (new enzymes, better enzyme derivatives, improved reaction designs and so on) and it seems that a massive industrial implementation of enzymes in antibiotic synthesis is approaching. In this review, we would like to make a critical discussion of these very interesting advances in the application of enzyme biocatalysts for the industrial synthesis of semi-synthetic antibiotics. Keywords: bioactive molecules, penicillin g, reactor design, solid synthesis, hydrolysis, organic solvents, phenylacetic acid (paa), antibiotics, thermodynamically controlled synthesis (tcs), thermostable enzymes

Direct calorimetry reveals large errors in respirometric estimates of energy expenditure

Knowledge of animal energetics is based largely upon indirect calorimetry, which is estimation of metabolic heat production by an organism from measurement of indices such as oxygen consumption or carbon dioxide production. Remarkably, indirect calorimetry has been validated by comparison to direct measurements of metabolic heat production (direct calorimetry) only for highly restricted conditions, primarily with a few species of medium-to-large mammals. Taxa with differing physiologies are little studied. For birds, for example, validations are limited to chickens and waterfowl exposed to mild environmental conditions and typically fasted for prolonged periods. Workers rely upon these restricted validations when studying animals ranging greatly in activity, phylogeny, body size and nutritional status. We tested the accuracy of respirometric estimates of energy expenditure by simultaneous indirect and direct calorimetry in a small mammal (the kangaroo rat Dipodomys merriami Mearns), a small bird (the dove Columbina inca Lesson) and a medium-sized bird (the quail Coturnix communis Linnaeus). We find that conventional respirometric estimates of energy expenditure may incorporate large errors (up to 38%) that are sufficient to call into question generalizations regarding patterns of animal energy use in many studies.

Confirming the pinking mechanism of PVC profiles in mild climatic conditions

AbstractPinking of TiO2‐pigmented PVC can be observed for profiles exposed to the mild environmental conditions of northern European countries. In a previous paper, the pinking phenomenon was accounted for at the molecular level by the formation of polyene sequences, which are not completely photooxidatively bleached in conditions of oxygen starvation. This causation has been confirmed by exposing to visible light in a SEPAP 12.24 apparatus profiles in which pinking was produced during 4 year‐weathering in N.W. France. The fast phototransformations in visible light of chloropolyenes in trans‐configurations leading to α‐chloropolyenes in cis‐configurations accounts for the conversion of pinking into limited graying. It appears that the first and more intense graying observed after the initial exposure to UV and visible light of profiles in the SEPAP 12.24 can be essentially attributed to the photoreduction products of lead stabilizers. Graying could be bleached through thermooxidation at 65°C, could not be converted into pinking, and has no environmental relevance.

Cultivo de embriões de tomate in vitro visando a introgressão de genes de Lycopersicon peruvianum em L. esculentum

Estudou-se diferentes protocolos de germinação e manutenção de híbridos interespecíficos (Lycopersicon esculentum X L. peruvianum) pela melhoria das condições de cultura in vitro bem como da aclimatação das plantas germinadas. Quanto à regeneração dos embriões, três formulações de meios de cultura para resgate de embrião foram avaliadas, em combinação com distintos períodos de tempo. A recuperação de híbridos interespecíficos foi influenciada pelo meio de cultura utilizado para o plaqueamento das sementes e pelo intervalo entre a polinização artificial e o plaqueamento. O meio HLH proporcionou os melhores resultados. O intervalo entre 25 e 35 dias após a polinização foi determinado como sendo o período ideal para recuperação. Para aclimatização, foram avaliadas plantas de L. esculentum, L. peruvianum, híbridos interespecíficos (F1) e das gerações RC1 e RC2. O processo de aclimatização foi influenciado pelo tamanho das gemas utilizadas na repicagem anterior à aclimatização, pelos materiais genéticos utilizados e pelo tempo de manutencão das plântulas em tubo de ensaio. A geracão F1 apresentou a melhor capacidade de aclimatização. O período ideal para aclimatização variou entre 26 e 35 dias após a repicagem em tubo de ensaio. As aclimatizações realizadas sob condições ambientais amenas, alcançaram êxito total quanto à sobrevivência das plântulas.

Thermoregulatory accuracy, precision, and effectiveness in two sand-dwelling lizards under mild environmental conditions

We investigated thermoregulation and habitat use in two sympatric lizard species of the family Phrynosomatidae (side-blotched lizards, Uta stansburiana, and sand-dune lizards, Sceloporus arenicolus) in southern New Mexico to determine whether thermoregulation was necessary and detectable under mild temperature conditions, and what behavioral mechanisms the lizards used to thermoregulate throughout their daily activity. We measured lizard temperature preference (Tsel) in a laboratory thermal gradient as well as field body temperature (Tb) at the study site. We then calculated several indices of thermoregulation to evaluate the effectiveness of thermoregulation for both species. In addition, we recorded and compared micro- and macro-habitat use for the two species; we also compared these habitats with randomly selected microsites. Uta stansburiana thermoregulated less precisely in a laboratory gradient than did S. arenicolus and had a slightly higher preferred temperature. Environmental thermal heterogeneity occurred at both micro- and macro-habitat spatial scales, allowing lizards to thermoregulate optimally for over 10 h/day. The two species maintained mean body temperatures within their selected temperature range throughout most of the day. Two indices of thermoregulatory effectiveness revealed that both species are effective thermoregulators, and thermoregulation was easily detectable throughout the day. Lizards used the behavioral mechanisms of microhabitat choice, posture, shuttling between sun and shade, and orientation to the sun to regulate Tb.

Industrial Synthesis of Semi-Synthetic β-Lactam Antibiotics: Recent Developments in Enzyme Biocatalysis for Improved and MORE Sustainable Processes

The production, under environmentally benign conditions, of efficient and more cost-effective anti-infective agents (available to the whole mankind) is one of most exciting dreams of the industrial medicinal chemistry. Semi-synthetic β-lactam antibiotics are very effective anti-infective agents. They are very stable and be can be used via oral delivering. They exhibit a very wide spectrum of anti-bacterial activity and minimal side-effects after being massively used for a very long time. In this way, we can assume that semi-synthetic β-lactam antibiotics are going to continue to be one of the key anti-infective agents for the next years. The condensation of natural or modified antibiotic nuclei with different acyl donor chains is one of the key steps for the industrial synthesis of these anti-infective agents. Up to now, these condensations are mainly carried out through classical chemical methods and it implies a number of economical, ecological and technological drawbacks (high energy requirements, many protection and deprotection steps, utilization of toxic methylene chloride as solvent, etc). Enzyme biocatalysts may be very useful to catalyze these selective condensations under very mild experimental and environmental conditions. In fact, the possibility to use enzymes to carry out such biotransformations, at laboratory scale, has been discussed and demonstrated a long time ago. However, industrial synthesis of beta-lactam antibiotic is still carried out via unfavorable chemical routes. In fact, enzymes have been not designed by nature to act in industrial reactors: they are usually very unstable, inhibited by substrates and products and they may have not ideal catalytic properties for industrial uses (high reaction rates, required selectivity, ability to reach quantitative synthetic yields, stability enough to run a number of reaction cycles, etc). These limitations of enzyme biocatalysis become even more significant mainly when the enzyme is going to be used with non-natural substrates, catalyzing non-natural processes and working under non conventional conditions. However, in the last ten years, a number of papers have reported substantial improvement of these enzymatic synthetic approaches (new enzymes, better enzyme derivatives, improved reaction designs and so on) and it seems that the massive industrial implementation of enzymes in antibiotic synthesis is very close. In these review, we would like to make a critical discussion of these very interesting advances in the application of enzyme biocatalyst for the industrial synthesis of semi-synthetic antibiotics.

Sodium replacement and fluid shifts during prolonged exercise in humans.

In the study presented here, we examined the affects of a close to complete replacement of sweat water and Na+ losses on fluid shifts during exercise. Six cyclists performed three 4-h rides at 55% of their peak oxygen uptake in a 20 degrees C environment while consuming 3.85 l of an 8% carbohydrate solution containing 5, 50 or 100 mEq.l-1 of Na+. Increases in Na+ intake reduced renal free water clearance from around 40 ml.h-1 to -8 and -121 ml.h-1 and led to a decrease in urine volume from approximately equal to 1.0 to 0.5 l (P < 0.05). In contrast, the 3.5-3.9 l fluid and 150-190 mEq Na+ losses in sweat were similar in each trial, as were the approximately equal to 80 mEq K+ losses in sweat and urine and the 282-288 mosmol.kg-1 plasma osmolalities. During the low-Na+ trial, plasma osmolality was maintained by a approximately equal to 1.3 l contraction of extracellular fluid (ECF) with the loss of approximately equal to 200 mEq Na+. However, in the other trials, approximately equal to 1.3 l of water was lost from the intracellular fluid. During the medium-Na+ trial, a loss of only approximately equal to 40 mEq Na+ maintained ECF volume, and during the high-Na+ trial, a gain of approximately equal to 160 mEq Na+ expanded the ECF by approximately equal to 0.8 l. However, corresponding changes in plasma volumes from -0.20 to 0.15 l had no effect on cardiovascular drift or thermoregulation. These data suggest that during prolonged exercise of moderate intensity under mild environmental conditions when sweat rates are approximately equal to 0.9 l.h-1, complete Na+ replacement maintains plasma volume and reduces dehydration, but when fluid intake matches sweat rate, has little effect on plasma osmolality.

Towards the prediction of pinking of PVC profiles in mild climatic conditions

AbstractPinking of TiO2‐pigmented PVC can be observed for profiles exposed to the mild environmental conditions of Northern European countries. In this paper, the pinking phenomenon is accounted for at the molecular level by the formation of polyene sequences which are not completely photooxidatively bleached under conditions of oxygen starvation. Photoreduction of TiO2 to give Ti(III) species accounts for greying which cannot be converted into pinking under mild thermooxidative conditions (65°C). The polyenic sequences which account for an initial greying after brief exposure in the SEPAP 12.24 apparatus can be converted into shorter, modified polyene sequences which explain the pinking. From the basic understanding gained, a predictive test has been designed and validated by comparison with results obtained under natural exposure conditions.

Fluid ingestion does not influence intense 1-h exercise performance in a mild environment

It is generally recommended that fluid be ingested during exercise at a rate that prevents body mass loss and prevents dehydration. It is, however, not known whether these recommendations are valid during intense endurance exercise in a mild environment. The purpose of this study was to examine the effect of fluid ingestion volume on heart rate (HR), rectal temperature, plasma electrolytes, and performance during intense endurance exercise at 21 degrees C. Eight well-trained men (26+/-1 yr; 79.6+/-3.5 kg; VO2peak = 5.05+/-0.17 L.min(-1) ; mean+/-SEM) cycled for 45 min at 80+/-1% VO2peak while receiving either no fluid replacement (NF), a volume of water that prevented body mass loss (FR-100 = 1.47+/-0.05 L), or 50% of this volume (FR-50 = 0.72+/-0.03 L). The 45-min exercise bout was followed immediately by a 15-min "all-out" performance ride. NF was associated with a 1.9+/-0.0% body mass loss, while FR-50 and FR-100 resulted in losses of 1.0 = 0.1% and 0.0+/-0.1%, respectively. Although values tended to be higher in NF, fluid ingestion had no significant effect on HR or rectal temperature during exercise. Reductions in plasma volume and increases in plasma sodium and potassium concentrations during exercise were largely unaffected by fluid ingestion. RPE increased to a similar extent during exercise in the three trials while a mild increase in the degree of stomach bloating/fullness was evident in FR-100. Work completed during the 15-min performance ride was similar in the three trials (NF: 273+/-8, FR-50: 267+/-8, FR-100: 269+/-9 kJ). There appears to be little benefit from ingesting water during intense 1-h cycling exercise in mild environmental conditions since such ingestion has no significant effect on HR, body temperature, plasma volume, plasma electrolytes, or performance.

Directed disruption of the tobacco ndhB gene impairs cyclic electron flow around photosystem I.

To evaluate the physiological significance of cyclic electron flow around photosystem (PS) I, we used a reverse genetic approach to focus on 11 chloroplast genes that encode homologs of mitochondrial complex I subunits (ndhA-K). Since their discovery, the exact function of the respiratory components in plant chloroplasts has been a matter of discussion. We disrupted one of these genes (ndhB) in tobacco by chloroplast transformation. Analysis of the transient increase in chlorophyll fluorescence after actinic light illumination and the redox kinetics of P700 (reaction center chlorophylls of PS I) suggest that the cyclic electron flow around PS I is impaired in the ndhB-deficient transformants. Transformants grew normally in a greenhouse, suggesting that the cyclic electron flow around PS I mediated by ndh gene products is dispensable in tobacco under mild environmental conditions.