Recent advances in double network hydrogels based on naturally-derived polymers: synthesis, properties, and biological applications.

Hydrogels composed of naturally-derived biopolymers have garnered significant research interest due to the bioavailability and biocompatibility of starting materials. However, translating these advantages to practical use is challenged by limitations of mechanical properties and stability of the resulting materials. The development of double network (DN) hydrogels has led to greatly enhanced mechanical properties and shows promise toward broadening the applications of conventional synthetic or natural hydrogels. This review highlights recently developed protein-based and polysaccharide-based DN hydrogels. For each biopolymer, we focus on a subset of DN hydrogels centered around a theme related to synthetic design or applications. Network structures and crosslinking mechanisms that endow enhanced mechanical properties and performance to the materials are discussed. Important applications, including tissue engineering, drug delivery, bioadhesives, wound healing, and wearable sensors, that arise from the inherent properties of the natural polymer or its combination with other materials are also emphasized. Finally, we discuss ongoing challenges to stimulate the discovery of new design principles for the future of DN hydrogels based on naturally-derived polymers for biological applications.

Recent progress in the microbial production of xylonic acid.

Interest in the production of renewable chemicals from biomass has increased in the past years. Among these chemicals, carboxylic acids represent a significant part of the most desirable bio-based products. Xylonic acid is a five-carbon sugar-acid obtained from xylose oxidation that can be used in several industrial applications, including food, pharmaceutical, and construction industries. So far, the production of xylonic acid has not yet been available at an industrial scale; however, several microbial bio-based production processes are under development. This review summarizes the recent advances in pathway characterization, genetic engineering, and fermentative strategies to improve xylonic acid production by microorganisms from xylose or lignocellulosic hydrolysates. In addition, the strengths of the available microbial strains and processes and the major requirements for achieving biotechnological production of xylonic acid at a commercial scale are discussed. Efficient native and engineered microbial strains have been reported. Xylonic acid titers as high as 586 and 171 g L-1 were obtained from bacterial and yeast strains, respectively, in a laboratory medium. Furthermore, relevant academic and industrial players associated with xylonic acid production will be presented.

Comparative study of indigenous chickens on the basis of their health and performance.

Three hundred crossbred chickens (at age of 11 wk) were randomly housed in 15 open-sided deep litter pens with 20 chickens in each pen under completely randomized design for a period of 9 wk. Before evaluating their hematobiochemical and carcass characteristics, the birds were provided with grower mash ad libitum throughout the experimental period. Blood samples were taken from each genotypic group (nanaff, Nanaff, and NanaFf), when the birds were 18 and 20 wk old, respectively, for the evaluation of hematobiochemical parameters. At the end of the trial, 15 chickens from each of the 3 genotypic groups were randomly selected and slaughtered to determine the carcass parameters. The findings from the study revealed that except for total cholesterol, spleen, and neck weight, there was no significant genotypic effect (P > 0.05) on hematobiochemical and carcass parameters measured. The nanaff genotype birds had significantly higher (P < 0.05) cholesterol levels than both Nanaff and NanaFf genotype birds, both of which did not differ significantly. The Nanaff had significantly (P < 0.05) higher spleen and neck weight than both the nanaff and NanaFf. The latter 2 did not differ significantly (P > 0.05). Also, hematobiochemical assays of all the birds were within normal range. From a health point of view, the indigenous naked neck genotype seems superior because its fat and cholesterol contents were low. Thus, it is strongly recommended that there should be a conscious effort to develop and commercialize the naked-neck and frizzled birds especially in developing countries.

Xylitol Production: Identification and Comparison of New Producing Yeasts.

Xylitol is a sugar alcohol with five carbons that can be used in the pharmaceutical and food industries. It is industrially produced by chemical route; however, a more economical and environmentally friendly production process is of interest. In this context, this study aimed to select wild yeasts able to produce xylitol and compare their performance in sugarcane bagasse hydrolysate. For this, 960 yeast strains, isolated from soil, wood, and insects have been prospected and selected for the ability to grow on defined medium containing xylose as the sole carbon source. A total of 42 yeasts was selected and their profile of sugar consumption and metabolite production were analyzed in microscale fermentation. The six best xylose-consuming strains were molecularly identified as Meyerozyma spp. The fermentative kinetics comparisons on defined medium and on sugarcane bagasse hydrolysate showed physiological differences among these strains. Production yields vary from YP/S = 0.25 g/g to YP/S = 0.34 g/g in defined medium and from YP/S = 0.41 g/g to YP/S = 0.60 g/g in the hydrolysate. Then, the xylitol production performance of the best xylose-consuming strain obtained in the screening, which was named M. guilliermondii B12, was compared with the previously reported xylitol producing yeasts M. guilliermondii A3, Spathaspora sp. JA1, and Wickerhamomyces anomalus 740 in sugarcane bagasse hydrolysate under oxygen-limited conditions. All the yeasts were able to metabolize xylose, but W. anomalus 740 showed the highest xylitol production yield, reaching a maximum of 0.83 g xylitol/g of xylose in hydrolysate. The screening strategy allowed identification of a new M. guilliermondii strain that efficiently grows in xylose even in hydrolysate with a high content of acetic acid (~6 g/L). In addition, this study reports, for the first time, a high-efficient xylitol producing strain of W. anomalus, which achieved, to the best of our knowledge, one of the highest xylitol production yields in hydrolysate reported in the literature.

Simultaneous improvement of grain yield and protein content in durum wheat by different phenotypic indices and genomic selection.

KEY MESSAGE: Simultaneous improvement of protein content and grain yield by index selection is possible but its efficiency largely depends on the weighting of the single traits. The genetic architecture of these indices is similar to that of the primary traits. Grain yield and protein content are of major importance in durum wheat breeding, but their negative correlation has hampered their simultaneous improvement. To account for this in wheat breeding, the grain protein deviation (GPD) and the protein yield were proposed as targets for selection. The aim of this work was to investigate the potential of different indices to simultaneously improve grain yield and protein content in durum wheat and to evaluate their genetic architecture towards genomics-assisted breeding. To this end, we investigated two different durum wheat panels comprising 159 and 189 genotypes, which were tested in multiple field locations across Europe and genotyped by a genotyping-by-sequencing approach. The phenotypic analyses revealed significant genetic variances for all traits and heritabilities of the phenotypic indices that were in a similar range as those of grain yield and protein content. The GPD showed a high and positive correlation with protein content, whereas protein yield was highly and positively correlated with grain yield. Thus, selecting for a high GPD would mainly increase the protein content whereas a selection based on protein yield would mainly improve grain yield, but a combination of both indices allows to balance this selection. The genome-wide association mapping revealed a complex genetic architecture for all traits with most QTL having small effects and being detected only in one germplasm set, thus limiting the potential of marker-assisted selection for trait improvement. By contrast, genome-wide prediction appeared promising but its performance strongly depends on the relatedness between training and prediction sets.

The distribution and host range of the banana Fusarium wilt fungus, Fusarium oxysporum f. sp. cubense, in Asia.

Fusarium oxysporum formae specialis cubense (Foc) is a soil-borne fungus that causes Fusarium wilt, which is considered to be the most destructive disease of bananas. The fungus is believed to have evolved with its host in the Indo-Malayan region, and from there it was spread to other banana-growing areas with infected planting material. The diversity and distribution of Foc in Asia was investigated. A total of 594 F. oxysporum isolates collected in ten Asian countries were identified by vegetative compatibility groups (VCGs) analysis. To simplify the identification process, the isolates were first divided into DNA lineages using PCR-RFLP analysis. Six lineages and 14 VCGs, representing three Foc races, were identified in this study. The VCG complex 0124/5 was most common in the Indian subcontinent, Vietnam and Cambodia; whereas the VCG complex 01213/16 dominated in the rest of Asia. Sixty-nine F. oxysporum isolates in this study did not match any of the known VCG tester strains. In this study, Foc VCG diversity in Bangladesh, Cambodia and Sri Lanka was determined for the first time and VCGs 01221 and 01222 were first reported from Cambodia and Vietnam. New associations of Foc VCGs and banana cultivars were recorded in all the countries where the fungus was collected. Information obtained in this study could help Asian countries to develop and implement regulatory measures to prevent the incursion of Foc into areas where it does not yet occur. It could also facilitate the deployment of disease resistant banana varieties in infested areas.

First Report of Spot Form of Net Blotch of Barley Caused by Pyrenophora teres f. maculata in Hungary.

A countrywide survey of fungal diseases of barley (Hordeum vulgare L.) was conducted from 2005 to 2009. Unusual leaf necrosis varying in shape from 1 × 2 mm necrotic flecks to 15 × 20 mm ovoid spots was found. Sometimes a chlorotic halo surrounding the dead area was observed. Lesions appeared on various cultivars in many commercial fields and experimental plots at a number of sampling sites. Symptomatic leaves were taken to the laboratory and incubated in a moist chamber at room temperature on the bench to induce sporulation of the pathogen. Conidiophores on the diseased tissues were single or in small groups, dark brown, and bore several hyaline-to-olive brown, almost cylindrical conidia with three to seven pseudosepta. Dimensions of conidia were 75.2 to 100.9 × 16.5 to 18.8 µm. Under a stereo microscope, single conidia were transferred aseptically from the leaves onto potato dextrose agar (PDA) with a sterile needle. Plates were kept in the dark at 20°C for 2 weeks. Cultures were gray to olive green, cottony, and did not form conidia and sexual structures. These characteristics indicated that the pathogens belonged to the genus Pyrenophora. Species identity was confirmed by PCR assays with specific primers developed for the barley pathogenic Pyrenophora spp. (3,4). Of 169 isolates, 41 were identified as P. teres Drechs. f. maculata Smed.-Pet., the spot form of net blotch pathogen (2), and two of them have been deposited at an international culture collection under accession nos. CBS 123929 and CBS 123930. The remaining isolates were either P. graminea or P. teres f. teres, the leaf stripe and net form of net blotch pathogens of barley, respectively. Pathogenicity of four P. teres f. maculata and two P. teres f. teres isolates from different regions was confirmed by Koch's postulates. Each isolate was grown on two 9-cm PDA plates at 22°C in darkness. After 10 days, aerial mycelia were scraped off, blended in 100 ml of sterile distilled water, and filtered through two layers of cheesecloth. Ten seedlings of cv. Botond were sprayed at the two-leaf stage with the mycelium suspension of each isolate and a water control until runoff. Seedlings were kept in a growth chamber at 100% relative humidity and 20°C in the dark for 24 h, then at 70% relative humidity and 24/20°C (day/night) with a 12-h photoperiod. Within 3 weeks, one to four brownish ovoid spots, typical of the spot form of net blotch symptoms, developed on the leaves inoculated with P. teres f. maculata. In contrast, the seedlings inoculated with P. teres f. teres exhibited characteristic net-like lesions, whereas the control plants sprayed with sterile water remained healthy. All strains were reisolated and identified by specific PCRs as described above. To our knowledge, this is the first report of the occurrence of P. teres f. maculata in Hungary. Resistance of barley against P. teres f. maculata and P. teres f. teres is inherited independently (1). Therefore, knowledge regarding the frequency and distribution of these pathogens is important for disease management and resistance breeding. References: (1) O. S. Afanasenko et al. J. Phytopathol. 143:501, 1995. (2) V. Smedegård-Petersen. Page 124 in: R. Vet. Agr. Univ. Yearbook. Copenhagen, 1971. (3) E. J. A. Taylor et al. Plant Pathol. 50:347, 2001. (4) K. J. Williams et al. Australas. Plant Pathol. 30:37, 2001.

Urinary aquaporin-2 excretion in preterm and full-term neonates.

The study was undertaken to define the role of aquaporin-2 (AQP2) in renal concentrating performance by measuring urinary AQP2 excretion and urine osmolality in healthy preterm and full-term neonates during early postnatal life. Random urine samples were obtained from 9 full-term newborn infants (mean birth weight 3,218 g, mean gestational age 39.2 weeks) at postnatal ages of 1, 3 and 5 days. Five premature infants with a mean birth weight of 1,570 g and mean gestational age of 30.6 weeks were studied at the end of the 1st week and then weekly up to the 6th week. Urine osmolality (Knauer osmometer), creatinine (modified Jaffé's method) and AQP2 concentrations (radioimmunoassay) were measured. In full-term neonates, urinary AQP2 excretion showed no consistent changes over the age period studied, while urine osmolality decreased significantly with advancing age. In premature infants, urinary AQP2 excretion remained practically unchanged during the first 4 weeks followed by an abrupt increase thereafter. Urine osmolality did not follow the developmental pattern of AQP2 excretion; its mean values varied only from 78 +/- 39 to 174 +/- 146 mosm/l during the experimental period. It is concluded that during the early postnatal period, urinary AQP2 excretion does not serve as a direct marker of the renal action of AVP and the renal capacity to concentrate urine.

The origin of eukaryotes: the difference between prokaryotic and eukaryotic cells.

Eukaryotes have long been thought to have arisen by evolving a nucleus, endomembrane, and cytoskeleton. In contrast, it was recently proposed that the first complex cells, which were actually proto-eukaryotes, arose simultaneously with the acquisition of mitochondria. This so-called symbiotic association hypothesis states that eukaryotes emerged when some ancient anaerobic archaebacteria (hosts) engulfed respiring alpha-proteobacteria (symbionts), which evolved into the first energy-producing organelles. Therefore, the intracellular compartmentalization of the energy-converting metabolism that was bound originally to the plasma membrane appears to be the key innovation towards eukaryotic genome and cellular organization. The novel energy metabolism made it possible for the nucleotide synthetic apparatus of cells to be no longer limited by subsaturation with substrates and catalytic components. As a consequence, a considerable increase has occurred in the size and complexity of eukaryotic genomes, providing the genetic basis for most of the further evolutionary changes in cellular complexity. On the other hand, the active uptake of exogenous DNA, which is general in bacteria, was no longer essential in the genome organization of eukaryotes. The mitochondrion-driven scenario for the first eukaryotes explains the chimera-like composition of eukaryotic genomes as well as the metabolic and cellular organization of eukaryotes.

A new aspect to the origin and evolution of eukaryotes.

One of the most important omissions in recent evolutionary theory concerns how eukaryotes could emerge and evolve. According to the currently accepted views, the first eukaryotic cell possessed a nucleus, an endomembrane system, and a cytoskeleton but had an inefficient prokaryotic-like metabolism. In contrast, one of the most ancient eukaryotes, the metamonada Giardia lamblia, was found to have formerly possessed mitochondria. In sharp contrast with the traditional views, this paper suggests, based on the energetic aspect of genome organization, that the emergence of eukaryotes was promoted by the establishment of an efficient energy-converting organelle, such as the mitochondrion. Mitochondria were acquired by the endosymbiosis of ancient alpha-purple photosynthetic Gram-negative eubacteria that reorganized the prokaryotic metabolism of the archaebacterial-like ancestral host cells. The presence of an ATP pool in the cytoplasm provided by this cell organelle allowed a major increase in genome size. This evolutionary change, the remarkable increase both in genome size and complexity, explains the origin of the eukaryotic cell itself. The loss of cell wall and the appearance of multicellularity can also be explained by the acquisition of mitochondria. All bacteria use chemiosmotic mechanisms to harness energy; therefore the periplasm bounded by the cell wall is an essential part of prokaryotic cells. Following the establishment of mitochondria, the original plasma membrane-bound metabolism of prokaryotes, as well as the funcion of the periplasm providing a compartment for the formation of different ion gradients, has been transferred into the inner mitochondrial membrane and intermembrane space. After the loss of the essential function of periplasm, the bacterial cell wall could also be lost, which enabled the naked cells to establish direct connections among themselves. The relatively late emergence of mitochondria may be the reason why multicellularity evolved so slowly.

Global issues of genetic diversity.

Genetic diversity within species is highly significant during their adaptation to environmental changes and, consequently, for their long-term survival. The genetic variability of species is also the basis for the evolution of higher levels of biodiversity, the evolution of species, and it might be an indispensible prerequisite for the functioning of our biosphere. Studies which promote understanding of the maintenance and the functional aspects of biodiversity at any level are therefore essential for the future welfare of mankind.

Role of metabolic activation in the sister chromatid exchange-inducing activity of ethyl carbamate (urethane) and vinyl carbamate.

Ethyl carbamate (EC, urethane) at 10(-2) M concentration induced more sister chromatid exchanges (SCEs) in cultured human peripheral blood lymphocytes in the absence of S9 mix than did 10(-2) M vinyl carbamate (VC), a possible proximate carcinogenic metabolite (Dahl et al., 1978) of EC. VC itself doubled SCE frequency over the control. In the presence of native S9 mix from Aroclor-induced rat liver, the SCE-inducing activity of VC was highly increased whereas that of EC was suppressed. This opposite effect of S9 mix on VC and EC seems to be due to two different factors. Activation of VC by the S9 fraction seems to be due to the presence of mixed-function oxidases in the S9 mix, because neither the native S9 fraction in the absence of co-factors nor the heat-inactivated S9 fraction in the incubation mixture led to the activation of VC. Deactivation of EC by S9 mix, on the other hand, seems to involve the presence of excess protein and/or substances of low molecular weight in the incubation mixture, because this deactivating effect did not change considerably when the S9 fraction was supplied in the absence of co-factors or when it originated from non-induced rat liver. Heat denaturation of the S9 fraction led to an increased deactivating effect on the SCE-inducing ability of EC. This result is in line with the assumption that reactive -SH groups in the S9 protein are at least partly responsible for the deactivation of EC by S9. Heat denaturation of the S9 fraction led to an about 1.5-fold increase in reactive -SH groups.

Population genetic basis of the evolutionary change.

Short introduction is given to population genetic treatment of the evolutionary change. The evolutionary change in the population is based upon the appearance (by mutation or immigration) of new genetic information. The proportion of this new information may increase or decrease by selection and/or random processes. The aid of population genetics is to formulate models in order to understand the essence of the evolutionary change. Some simple deterministic and stochastic single-locus models are quoted from elementary population genetic theory.

In vitro dissociation-recombination of malate dehydrogenase subunits in Corydalis solida.

Two allelic forms of NAD specific malate dehydrogenase were found in samples of a wild population of Corydalis solida. The dimeric nature and the origin of the heterodimeric form has been demonstrated by in vitro dissociation and recombination of the subunits detected by subsequent electrophoresis. The method is applicable for polyacrylamide gel electrophoresis of crude leaf extracts of individual MDH isozyme forms.

Urethane and hydroxyurethane induce sister-chromatid exchanges in cultured human lymphocytes.

Both urethane and hydroxyurethane induced sister-chromatid exchanges (SCE) in cultured human lymphocytes. Aroclor-induced rat-liver microsome fraction deactivated rather than activated these two agents in the lymphocyte system.

Platyzoma: a new look at an old link in ferns.

Record of a chromosome number of 2n = 76, unusual for pteridophytes, in Platyzoma microphyllum R. Br. emphasizes other unique features of this monotypic Queensland fern and provides new evidence of its possible relationships. Other characteristics of this plant, which are not known among terrestrial ferns, are incipient heterospory-having two sizes of spores and a dioecious condition of the gametophytes. These and other morphological features show relationships of Platyzoma to members of the Schizaeaceae and Marsileaceae and relationships of these families to the Polypodiaceae, in which it is treated under the subfamily Platyzomatoideae.