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Introduction Embryonic stem (ES) cells are considered a potentially advantageous source of hepatocytes for both transplantation and the development of bioartificial livers. However, the efficient large-scale generation of functional hepatocytes from ES cells remains a major challenge, especially for those methods compatible with clinical applications. Methods In this study, we investigated whether a large number of functional hepatocytes can be differentiated from mouse ES (mES) cells using a simulated microgravity bioreactor. mES cells were cultured in a rotating bioreactor in the presence of exogenous growth factors and hormones to form embryoid bodies (EBs), which then differentiated into hepatocytes. Results During the rotating culture, most of the EB-derived cells gradually showed the histologic characteristics of normal hepatocytes. More specifically, the expression of hepatic genes and proteins was detected at a higher level in the differentiated cells from the bioreactor culture than in cells from a static culture. On further growing, the EBs on tissue-culture plates, most of the EB-derived cells were found to display the morphologic features of hepatocytes, as well as albumin synthesis. In addition, the EB-derived cells grown in the rotating bioreactor exhibited higher levels of liver-specific functions, such as glycogen storage, cytochrome P450 activity, low-density lipoprotein, and indocyanine green uptake, than did differentiated cells grown in static culture. When the EB-derived cells from day-14 EBs and the cells’ culture supernatant were injected into nude mice, the transplanted cells were engrafted into the recipient livers. Conclusions Large quantities of high-quality hepatocytes can be generated from mES cells in a rotating bioreactor via EB formation. This system may be useful in the large-scale generation of hepatocytes for both cell transplantation and the development of bioartificial livers. [ABSTRACT FROM AUTHOR]

Introduction Embryonic stem (ES) cells are considered a potentially advantageous source of hepatocytes for both transplantation and the development of bioartificial livers. However, the efficient large-scale generation of functional hepatocytes from ES cells remains a major challenge, especially for those methods compatible with clinical applications. Methods In this study, we investigated whether a large number of functional hepatocytes can be differentiated from mouse ES (mES) cells using a simulated microgravity bioreactor. mES cells were cultured in a rotating bioreactor in the presence of exogenous growth factors and hormones to form embryoid bodies (EBs), which then differentiated into hepatocytes. Results During the rotating culture, most of the EB-derived cells gradually showed the histological characteristics of normal hepatocytes. More specifically, the expression of hepatic genes and proteins was detected at a higher level in the differentiated cells from the bioreactor culture than in cells from a static culture. Upon further growing the EBs on tissue-culture plates, most of the EB-derived cells were found to display the morphological features of hepatocytes, as well as albumin synthesis. In addition, the EB-derived cells grown in the rotating bioreactor exhibited higher levels of liver-specific functions, such as glycogen storage, cytochrome P450 activity, low-density-lipoprotein and indocyanine green uptake, than differentiated cells grown in static culture. When the EB-derived cells from day-14 EBs and the cells' culture supernatant were injected into nude mice, the transplanted cells were engrafted into the recipient livers. Conclusions Large quantities of high-quality hepatocytes can be generated from mES cells in a rotating bioreactor via EB formation. This system may be useful in the large-scale generation of hepatocytes for both cell transplantation and the development of bioartificial livers. [ABSTRACT FROM AUTHOR]

Spider webs are made of silk, the properties of which ensure remarkable efficiency at capturing prey. However, remaining on, or near, the web exposes the resident spiders to many potential predators, such as ants. Surprisingly, ants are rarely reported foraging on the webs of orb-weaving spiders, despite the formidable capacity of ants to subdue prey and repel enemies, the diversity and abundance of orb-web spiders, and the nutritional value of the web and resident spider. We explain this paradox by reporting a novel property of the silk produced by the orb-web spider Nephila antipodiana (Walckenaer). These spiders deposit on the silk a pyrrolidine alkaloid (2-pyrrolidinone) that provides protection from ant invasion. Furthermore, the ontogenetic change in the production of 2-pyrrolidinone suggests that this compound represents an adaptive response to the threat of natural enemies, rather than a simple by-product of silk synthesis: while 2-pyrrolidinone occurs on the silk threads produced by adult and large juvenile spiders, it is absent on threads produced by small juvenile spiders, whose threads are sufficiently thin to be inaccessible to ants. [ABSTRACT FROM AUTHOR]

A linear and non-linear analysis of a crossed-field gyrotron operating in the TE[sub m11] whispering gallery mode is presented. The starting oscillation condition, the effect of the internal conductor in a coaxial cavity on the cut-off frequency of the mode and the spacing between adjacent modes are considered. The effect of the applied voltage on the cyclotron frequency of the electron, the starting oscillation beam power and the electron efficiency are also considered. It is shown that 41% efficiency can be attained for m=2. These results are compareci with those in a cylindrical cavity. [ABSTRACT FROM AUTHOR]

Nephila are known for the greatest degrees of sexual size dimorphism among orb weaving spiders (Araneoidea) and thus among terrestrial animals. However, a meaningful quantification of the dimorphism is lacking and the proximate developmental mechanisms of female gigantism are poorly understood, being attributed solely to female delayed maturation. Here we show that females in the giant wood spider Nephila pilipes (Fabricius 1793) become giants through facultative post-maturity molting, a phenomenon resulting in female carapaces on average 4.27 times longer than males' (ranging from 3 to 6.4 times), and female mass averaging 125 times the male's (ranging from 28 to 502 times). Although the small males follow a typical developmental pathway and reach maturity with their final molt, the females mature at varying sizes and instars and then continue to grow by molting the entire exoskeleton except their genitals. The newly discovered phenomenon of additional, single-sex, adult, non-genital molting may represent a critical developmental adaptation that facilitates female gigantism in Nephila as a response to fecundity selection. [ABSTRACT FROM AUTHOR]

Behavioral plasticity has been proposed as a means by which animals alter their phenotypes in response to changing conditions. Animals may display behavioral plasticity as a consequence of environmental variation. The detritus-based, bell-shaped cobweb spider Campanicola campanulata is an ideal model to study behavioral plasticity, because its web architecture is easy to be quantified, and the functions of different parts of the web are clear. Though the plasticity of cobweb architecture has been reported in a few species, retreats as important defensive structures have rarely been considered before because retreats in most cobwebs are relatively small compared with the web size. We studied the web-building behaviors of C. campanulata under different feeding regimes. We set up 3 spider treatments with different feeding conditions: marginally well fed, moderately well fed, and extremely well fed, and observed the differences in the web architecture among them. In addition, we measured the mechanical properties of anchor silk, and also calculated the foraging and defense investment of the spiders. The results showed that marginally well-fed spiders build cobwebs with significantly longer length of anchor silk, lower retreat to the ground, more number and longer gumfooted lines, and larger capture area, while extremely well-fed spiders build cobwebs with significantly bigger retreat volume and higher height of retreat to the ground. In addition, marginally well-fed spiders invest significantly less during cobweb construction. However, there was no significant difference between the breaking force and elongation at break in anchor silk among different treatments. These results demonstrated that marginally well-fed spiders invest more in foraging, and extremely well-fed spiders invest more in defense, and the spider made a balance between foraging and predator avoidance in response to changes in physiological state. Our study strengthens the current understanding of web construction in cobweb spiders, especially those facing high costs during retreat construction. [ABSTRACT FROM AUTHOR]

As one of the most important invasive and destructive pests in the world, the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) reduces crop yield and causes economic loss. It is critical to find an appropriate controlling approach. This study aimed to determine the insecticidal activities of botanical insecticides (30% tea saponin, 0.6% matrine and a mixture thereof) on fall armyworm larvae, as well as the effects of sublethal concentrations of an optimal ratio of the mixture, on the survival rate, developmental duration, pupation rate, emergence rate, and body weight of fall armyworm. In addition, we evaluated the control effect of the insecticides (30% tea saponin, 0.6% matrine, optimal ratio of mixture along with 0.3% azadirachtin and 36% chlorfenapyr) and toxicity to natural enemies in field conditions. The results showed that all botanical insecticides and mixtures were toxic, and the insecticidal bioactivity of 10:1 volume ratio mixture was the highest at 96 hours, with a median lethal concentration (LC50) of 56.561 mg/mL. Meanwhile, the sublethal concentration of a 10:1 volume ratio of the mixture significantly affected the survival rate, prolonged developmental duration and reduced emergence rates and pupal weights, but it did not affect the pupation rates of fall armyworm. Furthermore, it has harmless or slightly harmful effects on natural enemies. Our study provides a novel environmentally friendly and natural enemy-friendly approach to controlling fall armyworms. [ABSTRACT FROM AUTHOR]

In order to study the roles of members of HKT gene family in wheat, TaHKTl; 2 was isolated by using homologous cloning strategy and screening genomic BAC library. TaHKTl-, 2 genes were mapped on chromosomes 7A, 7B and 7D, named as TaHKTl-, 2-7A, TaHKTl; 2-7B, and TaHKTl-, 1-1D, respectively. TaHKTl; 2 and TaHKTl; 1 had the same genetic structure, composed of three exons and two introns, and formed a cluster with TaHKTl; 1 on the phylogenetic tree of plant HKT transporters. The coding sequences of TaHKTl-, 1-1A, TaHKTl; 1-7B, and TaHKTl; 1-1D were 1 602, 1 602 and 1 596 bp long, respectively, but TaHKTl; 1-7D cDNA sequence was not isolated by RT-PCR in eight wheat varieties. The natural diversity of TaHKTl; 2 genes was analyzed by cloning and sequencing from 12 wheat varieties. The results showed that TaHKTl;2-7A was found to be more diverse than TaHKTl; 1-1B and TaHKTl; 1-1D. Only a few bases changed in the alleles of TaHKTl; 2 genes in wheat. No amino-acid natural variation lay in the P-loops of deduced protein sequences of all alleles of TaHKTl; 2 in 12 wheat varieties. The identity of coding sequences was much higher than that of 5' flanking regions of TaHKTl; 2 genes. TaHKTl; 2 might be selected over the course of wheat domestication and belonged to domestication gene. [ABSTRACT FROM AUTHOR]

Sexual conflict is common in animals, and female sexual cannibalism represents an extreme form of sexual conflict. Males in many species have evolved a variety of strategies to circumvent or decrease the risk of female sexual cannibalism. Opportunistic mating, by which a male mates with a female when she is disturbed or when she is feeding or undertaking moulting, is one of such kinds of strategies, and widely occurs in many animals, especially in spiders. However, whether the occurrence of male opportunistic mating depends on the intensity of female sexual cannibalism remains largely unexplored. We predicted a positive correlation between them. In this study, we tested this prediction by performing a series of mating trials in the laboratory using 3 species of web-building spiders with different intensities of female sexual cannibalism: Nephila pilipes , Nephilengys malabarensis , and Parasteatoda tepidariorum. We found that the occurrence of male opportunistic mating was positively, though not statistically significantly, correlated with the intensity of female sexual cannibalism, thus supporting our hypothesis. All together, we provide evidence that male opportunistic mating may have evolved to respond to the selection pressure posed by female sexual cannibalism. [ABSTRACT FROM AUTHOR]

Background: Males usually produce mating plugs to reduce sperm competition. However, females can conceivably also produce mating plugs in order to prevent unwanted, superfluous and energetically costly matings. In spiders-appropriate models for testing plugging biology hypotheses-mating plugs may consist of male genital parts and/or of amorphous covers consisting of glandular or sperm secretions. In the giant wood spider Nephila pilipes, a highly sexually dimorphic and polygamous species, males are known to produce ineffective embolic plugs through genital damage, but nothing is known about the origin and function of additional conspicuous amorphous plugs (AP) covering female genitals. Methodology: We tested alternative hypotheses of the nature and function of AP in N. pilipes by staging mating trials with varying degrees of polyandry. No APs were ever formed during mating trials, which rules out the possibility of male AP formation. Instead, those females that oviposited produced the AP from a liquid secreted during egg sac formation. Polyandrous females were more likely to lay eggs and to produce the AP, as were those that mated longer and with more total insertions. Our further tests revealed that, in spite of being a side product of egg sac production, AP, when hardened, prevented any subsequent copulation. Conclusions: We conclude that in the giant wood spider (Nephila pilipes), the amorphous mating plugs are not produced by the males, that repeated copulations (most likely polyandrous) are necessary for egg fertilization and AP formation, and that the AP represents a female adaptation to sexual conflict through prevention of unwanted, excessive copulations. Considering the largely unknown origin of amorphous plugs in spiders, we predict that a similar pattern might be detected in other clades, which would help elucidate the evolutionary interplay of various selection pressures responsible for the origin and maintenance of mating plugs. [ABSTRACT FROM AUTHOR]

Nanosecond-pulse breakdown indicates special characteristics depending on the pulse rise-time and duration. Based on a repetitive nanosecond-pulse generator, breakdown phenomena of parallel-plane gaps in nitrogen were investigated with single pulse and repetitive bursts under different gap conditions. The relationships between applied voltage, pulse repetition frequency, breakdown time lag, repetitive pulse stress time and the number of applied pulses are presented. The curves regarding E-field strength, breakdown time lag and gas pressure are also obtained. The experimental results show that breakdown characteristics with repetitive nanosecond-pulses are different from that with single pulse. Repetitive nanosecond-pulse breakdown is concerned with the accumulation effect that is attributed to residual ions and metastable species survived from previous pulses. in addition, a modified empirical formula about E-field strength, breakdown time lag and gas density is given for the breakdown data. [ABSTRACT FROM AUTHOR]

Based on a Marx generator and a coaxial pulse forming line, an experimental investigation of surface flashover characteristics in vacuum is conducted by using nanosecond pulses of 10 ns rise time and 30 us full width at half maximum (FWHM). Insulator dielectrics chosen for this investigation are Teflon, PMMA and Nylon. The tested factors include gas pressure, cone angle of conical frustum, diameter and length of cylindrical insulator, material and shape of electrode, and contact style between insulator and electrodes. The effects of these parameters on the surface flashover characteristics are described and analyzed in this paper. In addition, the character of flashover time lag in the nanosecond range, and surface flashover theory in vacuum charged by nanosecond pulses are also discussed. [ABSTRACT FROM AUTHOR]

Repetitive pulsed power is becoming an important area of high-power technology. Dielectric failure data concerning electrical insulation play a basic role, but breakdown has been inadequately studied for the repetitive nanosecond-pulse conditions. This paper is concerned with the breakdown characteristics of tip-plane gas gaps under repetitive burst conditions at variant repetition rates (rep-rates) and diverse gap distances. The relationship among applied voltage, breakdown time lag, number of applied pulses to breakdown, repetitive pulse stress time, and rep-rates is presented. The experimental results presented show that breakdown polarity dependence is not distinct. The data also indicate that significant concentrations of excited particles and residual charges would be formed during the consecutive nanosecond pulses and would present a memory effect that affects the development of gas breakdown. In addition, the detachment of negative ions, cathode collision of positive ions, and deexcitation of metastable species can provide the source of avalanche-initiating electrons. [ABSTRACT FROM AUTHOR]

This paper presents the investigation of a mirror system of a quasi-optical (QO) mode converter for a high-power coaxial-cavity gyrotron. The mirror system consists of three mirrors. The first mirror is a quasi-elliptical one. Based on the Katsenelenbaum-Semenov Algorithm (KSA), the second and the third mirrors are iteratively optimized as adapted phase-correcting mirrors to transform the outgoing wave beam into a fundamental Gaussian structure. The investigation shows that the focal length of the quasi-elliptical mirror has a great influence on the optimized conversion efficiency, and, hence, it should be chosen to match the asymptotic beam growth (ABG) angle well in order to obtain high conversion efficiency. The design of a mirror system has been performed for a 2 MW, continuous wave (CW), 170 GHz, and TE34,19-mode coaxial-cavity gyrotron, which is under development at Forschungszentrum Karlsruhe, Germany. Taking into account the size of the mirrors and the conversion efficiency, a mirror system has been designed with a conversion efficiency of 98.3%. [ABSTRACT FROM AUTHOR]

This paper illustrates images of dielectric-barrier discharge (DBD) excitated by repetitive unipolar nanosecond pulses in atmospheric air. Different images are obtained for three barrier dielectrics and various gap lengths. Discharge images show that the nanosecond-pulse DBD observed with the eye is a diffuse glowlike mode when air gap is 2 mm; clear filamentary discharge is seen with the eye in the case of air gap of 8 mm. The results show that gap length and dielectrics are the important factors influencing the transition from diffusive to filamentary discharges. [ABSTRACT FROM AUTHOR]