Dietary fibres,fibre analogues,and glucose tolerance: importance of viscosity.

To define the type of dietary fibre of fibre analogue with the greatest potential use in diabetic treatment, groups of four to six volunteers underwent 50-g glucose tolerance tests (GTT) with and without the addition of either guar, pectin, gum tragacanth, methylcellulose, wheat bran, or cholestyramine equivalent to 12 g fibre. The addition of each substance significantly reduced blood glucose concentration at one or more points during the GTT and generally reduced serum insulin concentrations. The greatest flattening of the glucose response was seen with guar, but this effect was abolished when hydrolysed non-viscous guar was used. The reduction in the mean peak rise in blood glucose concentration for each substance correlated positively with its viscosity (r = 0.926; P less than 0.01), as did delay in mouth-to-caecum transit time (r = 0.885; P less than 0.02). Viscous types of dietary fibre are therefore most likely to be therapeutically useful in modifying postprandial hyperglycaemia.     

Factors influencing the efficiency of constructed wetlands used for the treatment of intensive trout farm effluent

In this paper the factors influencing treatment performance of subsurface flow constructed wetlands (SSF wetlands) treating aquaculture effluents were identified and quantified. The financial impact of advanced aquaculture effluent treatment with SSF wetlands was calculated.It is the first long-term, commercial-scale trial of SSF wetland treatment for effluents from intensive trout farming, a highly diluted effluent at very high flow rates (mean total phosphorous concentration 0.34 mg L^?1 at 14.3 L s^?1). The 12-month survey provided the opportunity to generate calculation fundamentals for the commercial application of SSF wetlands for aquaculture. Treatment efficiencies of up to 75–86% for total ammonia nitrogen (TAN), biological oxygen demand (BOD₅) and total suspended solids (TSS) were achieved. The daily area retention rate per square meter wetland area was between 2.1 and 4.5 g for TAN and between 30 and 98 g for TSS.The performance of the six wetland cells comprising three replicated hydraulic loading groups (14.5, 6.9, 3.3 m³ m^?2 day^?1) was monitored, offering the possibility to identify factors influencing treatment efficiency through multifactor analysis. These factors turned out to be nutrient inflow concentration, hydraulic loading rate and accumulation of TSS within the wetland bed, the only time-dependent factor. Factors such as vegetation period and fish harvesting were shown to be of significant but negligible importance.Inflow nutrient concentration is determined by production intensity, husbandry conditions, feed quality and any pre-treatment of effluent. Hydraulic load is determined by the space and budget available for SSF construction. TSS accumulation in the wetland is influenced by pre-treatment of the solid fraction prior to the wetland and determines the wetland service lifetime.From these factors the expenses of commercial wetland application can be estimated, leading to a cost increase around €0.20 kg^?1 fish produced (less than 10% of production costs) and therefore confirm the commercial feasibility of SSF wetland treatment.     

Application of biological activated carbon as a low pH biofilter medium for gas mixture treatment

Packing material is a crucial component of a bioreactor as it is the microbial population's habitat. This study assessed potential improvements to current biofiltration processes by investigating use of a novel support medium. Biological activated carbon (BAC) with microorganisms growing on granular activated carbon can produce a novel medium in which both adsorption and biodegradation contribute to pollutants removal. Investigation of carbon characteristics demonstrated that BAC was an ideal packing medium for biofiltration. The application of the novel packing medium for gas mixture treatment was evaluated in a low pH biofilter. Results demonstrated that BAC biofilter obtained high removal efficiency for both H(2)S and toluene. The removal mechanisms of BAC were investigated after the biofilter operation and it demonstrated that the performance of the BAC system was mainly controlled by the additive contributions of two removal mechanisms - adsorption and biodegradation. This study also indicated the potential for simultaneous treatment of hydrogen sulfide and toluene at low pH condition.     

Dependence of rifabutin properties and liposome entrapment on pH of the medium]

Rifabutin solubility within pH 3.0 to 11.0 was determined. Potentiometry, spectrophotometry and computation revealed ionization of three groups with pKa 3.5, 6.5 and 9.5 in the rifabutin molecule. On the basis of the pKa values of certain fragments of the rifabutin molecule computed by the ACD/pKa programme they were related to ionization of the following groups: imidazole residue nitrogen, aromatic hydoxyl and piperidin nitrogen respectively. Interaction of rifabutin with model membranes, i. e. large unilamellar vesicules was studied. At lower pH of the medium, entrapment of rifabutin to the large unilamellar vesicules increased that was evident of satisfactory correlation with the decrease in the rifabutin distribution coefficient in the system multilamellar vesicules/water under the experimental conditions.     

Effect of pH and calcium of the surrounding medium on electrical activity of the isolated muscle spindle

The effect of pH and the calcium ions of the surrounding medium on the receptor potential and unit activity of the isolated frog muscle spindle was investigated. With a decrease in pH of the medium the amplitude and duration of the hyperpolarization phase of the receptor potential increased and the amplitude of its depolarization phase decreased. The frequencies of the spontaneous and evoked activity were reversibly reduced under these conditions. A change in pH of the surrounding medium toward the alkaline side led to a decrease in the amplitude and duration of the hyperpolarization phase of the receptor potential. The firing rate initially increased and then decreased to 30–50% of normal. An increase in the calcium concentration in an alkaline medium led to an increase, but in an acid and normal medium to a decrease, in firing rate. The observed changes in electrical activity of the muscle spindle in solutions can be explained by changes in the velocity of active (electrogenic) and passive transport of sodium and calcium ions.     

Effect of carbon source and pH of the growth medium on spore germination inPhycomyces blakesleeanus

Phycomyces blakesleeanus sporangiospores responded differently to activation by physical and chemical stimuli. Spores that were physically (heat shock) activated or chemically (ammonium acetate) activated germinated and grew at pH 4.5 with the hexoses glucose, fructose, galactose, andN-acetylglucosamine, and with glycerol and amino acids. Under these conditions, physically activated spores showed a lower, although significant growth with the hexoses fructose, galactose,N-acetylglucosamine and with glycerol. On the other hand, physically activated spores incubated at alkaline pH (pH 7.3) required glucose to germinate; a requirement not observed with chemically activated spores, which showed significant growth in the other hexoses tested. Both physically and chemically activated spores incubated at pH 7.3 were unable to germinate and grow with amino acids and glycerol. These results suggest that there are different targets for activation of the spores by physical and chemical treatments. The levels of the fermentative enzymes alcohol dehydrogenase and lactate dehydrogenase and of the oxidative enzyme NAD⁺-isocitrate dehydrogenase were higher in cells grown at pH 4.5 in medium containing glucose; however, alcohol dehydrogenase and lactate dehydrogenase appear not to be affected by a change in the pH of the growth medium.     

Physiological properties of Saccharomyces cerevisiae during sine-modulated and stepwise changes in the medium pH

The responses of a chemostat Saccharomyces cerevisiae culture (D = 0.1 h-1) to a stepwise increase or decrease in the pH of the medium were shown to be asymmetric. When the pH was lowered from 6.5 to a value above 0.3, the rates of oxygen uptake and carbon dioxide evolution rose for a sort period of time whereas the optical density of the culture fell down. The detected changes in the properties of the culture were identical with those which had been observed in the course of spontaneous undamped oscillations in the physiological parameters of the continuous C. cerevisiae culture. Apparently, in both cases, the energy status of cells changed when the oxidative type of metabolism was substituted by fermentation. When the pH of the medium was elevated within the same range (4.7-6.5), the response of the culture was three times as low and its properties changed in the opposite direction. When the pH of the medium was changed in a cyclic sinusoidal manner, oscillations in the physiological characteristics of the culture, identical with spontaneous oscillations were induced at certain values of the amplitude and the frequency of pH changes.     

Polymerizing the fibre between bacteria and host cells: the biogenesis of functional amyloid fibres

Amyloid fibres are proteinaceous aggregates associated with several human diseases, including Alzheimer's, Huntington's and Creutzfeldt Jakob's. Disease-associated amyloid formation is the result of proteins that misfold and aggregate into β sheet-rich fibre polymers. Cellular toxicity is readily associated with amyloidogenesis, although the molecular mechanism of toxicity remains unknown. Recently, a new class of 'functional' amyloid fibres was discovered that demonstrates that amyloids can be utilized as a productive part of cellular biology. These functional amyloids will provide unique insights into how amyloid formation can be controlled and made less cytotoxic. Bacteria produce some of the best-characterized functional amyloids, including a surface amyloid fibre called curli. Assembled by enteric bacteria, curli fibres mediate attachment to surfaces and host tissues. Some bacterial amyloids, like harpins and microcinE492, have exploited amyloid toxicity in a directed and functional manner. Here, we review and discuss the functional amyloids assembled by bacteria. Special emphasis will be paid to the biology of functional amyloid synthesis and the connections between bacterial physiology and pathology.     

pH-sensitive polymer blends used as coating materials to control drug release from spherical beads: importance of the type of core

The aim of this study was to coat theophylline-loaded spherical beads with pH-sensitive polymer blends to control the resulting drug release kinetics. Various mixtures of ethylcellulose (water-insoluble) and Eudragit L (methacrylic-acid-ethyl-acrylate-copolymer; water-insoluble/water-soluble below/above pH 5.5) were used as coating materials. Two types of theophylline cores were studied: pure drug matrixes and theophylline-layered sugar cores. Importantly, the type of core significantly affected the resulting drug release patterns. Interestingly, not only the slope, but also the shape of the release curves was altered, indicating changes in the underlying mass transport mechanisms, despite of the identical composition of the polymeric coatings. The observed differences could be explained based on the physicochemical properties of the film coatings and the swelling behavior of the beads upon exposure to the release media. Using this knowledge the development/optimization of this type of drug delivery system can be facilitated and the safety of the pharmacotherapies be improved.     

Factors influencing virus inactivation and retention of platelet properties following treatment with aminomethyltrimethylpsoralen and ultraviolet A light.

A wide variety of viruses are inactivated by psoralen compounds in the presence of ultraviolet A light (UVA). Use of aminomethyltrimethylpsoralen (AMT) and UVA is being evaluated as a method to inactivate viruses that may be present in platelet suspensions prepared for transfusion. Studies have been conducted to assess how variation in various environmental parameters influences the extent of viral inactivation and the retention of platelet properties. Most notably, it was determined that increasing levels of plasma progressively inhibited the inactivation of model viruses. As a result, experiments were routinely conducted at a plasma level of approximately 14.5%, using 40 micrograms/ml AMT, which was determined to be optimal when using this reduced plasma level. The reduced plasma level was achieved by dilution with a nonplasma medium that has been shown to be satisfactory for storage of platelets. Under these conditions, about 5 logs of vesicular stomatitis virus (VSV), pseudorabies, and phi 6 inactivation were achieved. Variation of platelet and leukocyte counts, within normal levels, had a minimal effect on extent of viral inactivation. Although oxygen level (mean levels, 97.9 mm Hg versus 19.2 mm Hg) had only a small influence on viral inactivation with 2.4, 4.8, and 7.2 J/cm2 of UVA (equivalent to 1-3 minutes of exposure), in vitro platelet properties, such as medium pH, morphology characteristics, and aggregation response, were better retained with a longer exposure time at the reduced oxygen level. With normal oxygen (97.9 mm Hg), platelet properties declined substantially relative to untreated controls (no UVA, no AMT) on exposure to 4.8 J/cm2. Our studies have identified two sets of conditions that provide about 5 logs of virus inactivation without extensively altering platelet in vitro properties.     

The capacity of growing algal cells to affect the pH and the buffering properties of the medium

Supernatants from cultures of green high-temperature algae,Chlorella 7-11-05 and Stichococcus 6-17-35, were used to obtaintitration curves and to calculate buffer indexes (ß).It was generally observed that the peak of buffering activityin growing cultures shifted to the pH characteristic of thepK of the newly generated buffer(s). Depending on the experimentalconditions and the age of the culture, the buffering capacityat its peak increased up to 4–5 times of the value forthe original medium. Buffering capacity of algal cells was demonstratedfor both strains grown in the media originally buffered eitherwith phosphate or with Tris and for cultures of different agesincluding those of the young synchronized cells. The capacityof growing cells to drastically affect the pH and/or the bufferingcharacteristics of the medium indicates that the role of thebuffer originally employed in a particular medium may oftenextend for a relatively short period of time after which thebuffer system(s) produced by the cells play a more importantpart. (Received May 18, 1971; )     

Theoretical study on the molecular and electronic properties of some substances used for diabetes mellitus treatment

Diabetes mellitus (DM) is a disease that affects a large number of people, and the number of problems associated with the disease has been increasing in the past few decades. These problems include cardiovascular disorders, blindness and the eventual need to amputate limbs. Therefore, the quality of life for people living with DM is less than it is for healthy people. In several cases, metabolic syndrome (MS), which can be considered a disturbance of the lipid metabolism, is associated with DM. In this work, two drugs used to treat DM, pioglitazone and rosiglitazone, were studied using theoretical methods, and their molecular properties were related to the biological activity of these drugs. From the results, it was possible to correlate the properties of each substance – particularly electronic properties – with the biological interactions that are linked to their pharmacological effects. These results suggest that there are future prospects for designing or developing new drugs based on the correlation between theoretical and experimental properties.     

Alpine vascular plant species richness: the importance of daily maximum temperature and pH

Species richness in the alpine zone varies dramatically when communities are compared. We explored (i) which stress and disturbance factors were highly correlated with species richness, (ii) whether the intermediate stress hypothesis (ISH) and the intermediate disturbance hypothesis (IDH) can be applied to alpine ecosystems, and (iii) whether standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone. Species numbers and standing crop were determined in 14 alpine plant communities in the Swiss Alps. To quantify the stress and disturbance factors in each community, air temperature, relative air humidity, wind speed, global radiation, UV-B radiation, length of the growing season, soil suction, pH, main soil nutrients, waterlogging, soil movement, number of avalanches, level of denudation, winter dieback, herbivory, wind damage, and days with frost were measured or observed. The present study revealed that 82% of the variance in␣vascular species richness among sites could be explained by just two abiotic factors, daily maximum temperature and soil pH. Daily maximum temperature and pH affect species richness both directly and via their effects on other environmental variables. Some stress and disturbance factors were related to species richness in a monotonic way, others in an unimodal way. Monotonic relationships suggest that the harsher the environment is, the fewer species can survive in such habitats. In cases of unimodal relationships (ISH and IDH) species richness decreases at both ends of the gradients due to the harsh environment and/or the interaction of other environmental factors. Competition and disturbance seemed only to play a secondary role in the form of fine-tuning species richness in specific communities. Thus, we concluded that neither the ISH nor the IDH can be considered useful conceptual models for the alpine zone. Furthermore, we found that standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone, even though there is no direct causality.     

Factors influencing the distribution of Azorean mountain vegetation: implications for nature conservation

In order to understand the main ecological factors that influence the distribution of mountain vegetation in Azores and to use it as a model for nature conservation, a study on Santa Bárbara Mountain on Terceira Island was performed. A multivariate analysis was done on vegetation data and the abiotic factors governing the vegetation pattern are discussed. The major factors contributing to the observed vegetation patterns are wind exposure, soil water saturation and historical human impacts. The vegetation analysis showed that Azorean Mountain habitats have a high variation of vegetation structure as a result of the habitat heterogeneity and the extreme ecological conditions. Using the co-dominant plants as indicator species, eco-zones are distinguished, characterized by the combination of different ecological–human factors which contribute to the distribution of specific types of natural vegetation communities. The studies of vegetation distribution give important information about the relation between vegetation and landscape that is essential for conservation, restoration proposals and landscape planning. Azores terrestrial Natura 2000 sites are largely dominated by mountain vegetation, therefore this work provides essential background data for the management plans of these sites.