Environmental scanning electron microscopy offers real-time morphological analysis of liposomes and niosomes

Liposomes have been imaged using a plethora of techniques. However, few of these methods offer the ability to study these systems in their natural hydrated state without the requirement of drying, staining, and fixation of the vesicles. However, the ability to image a liposome in its hydrated state is the ideal scenario for visualization of these dynamic lipid structures and environmental scanning electron microscopy (ESEM), with its ability to image wet systems without prior sample preparation, offers potential advantages to the above methods. In our studies, we have used ESEM to not only investigate the morphology of liposomes and niosomes but also to dynamically follow the changes in structure of lipid films and liposome suspensions as water condenses on to or evaporates from the sample. In particular, changes in liposome morphology were studied using ESEM in real time to investigate the resistance of liposomes to coalescence during dehydration thereby providing an alternative assay of liposome formulation and stability. Based on this protocol, we have also studied niosome-based systems and cationic liposome/DNA complexes.     

Mating status regulates post‐mating refractory period in Striacosta albicosta females

In polyandrous insect species, males may transfer substances to reduce sperm competition by affecting female sexual receptivity. In this study, we determined the incidence of polyandry in females of Western bean cutworm (WBC), Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), and investigated the influence of both previous female and male mating history on the duration of mating, the female refractory period, and subsequent calling behavior of females under controlled laboratory conditions. The mating status of WBC males influenced mating duration, with copulations involving previously mated males taking longer, possibly related to the time required to produce an ejaculate. The duration of the female refractory period and the onset time of recalling during the scotophase were both affected by female mating history, but not by that of the males. Females had a shorter refractory period and resumed calling activity earlier after their second and third matings than after their first mating. The earlier onset of calling by previously mated females could reduce competition with virgin females and their shorter refractory period could explain the high incidence of polyandry observed in nature.     

Impact of QTL properties on the accuracy of multi-breed genomic prediction

Background

Although simulation studies show that combining multiple breeds in one reference population increases accuracy of genomic prediction, this is not always confirmed in empirical studies. This discrepancy might be due to the assumptions on quantitative trait loci (QTL) properties applied in simulation studies, including number of QTL, spectrum of QTL allele frequencies across breeds, and distribution of allele substitution effects. We investigated the effects of QTL properties and of including a random across- and within-breed animal effect in a genomic best linear unbiased prediction (GBLUP) model on accuracy of multi-breed genomic prediction using genotypes of Holstein-Friesian and Jersey cows.

Methods

Genotypes of three classes of variants obtained from whole-genome sequence data, with moderately low, very low or extremely low average minor allele frequencies (MAF), were imputed in 3000 Holstein-Friesian and 3000 Jersey cows that had real high-density genotypes. Phenotypes of traits controlled by QTL with different properties were simulated by sampling 100 or 1000 QTL from one class of variants and their allele substitution effects either randomly from a gamma distribution, or computed such that each QTL explained the same variance, i.e. rare alleles had a large effect. Genomic breeding values for 1000 selection candidates per breed were estimated using GBLUP modelsincluding a random across- and a within-breed animal effect.

Results

For all three classes of QTL allele frequency spectra, accuracies of genomic prediction were not affected by the addition of 2000 individuals of the other breed to a reference population of the same breed as the selection candidates. Accuracies of both single- and multi-breed genomic prediction decreased as MAF of QTL decreased, especially when rare alleles had a large effect. Accuracies of genomic prediction were similar for the models with and without a random within-breed animal effect, probably because of insufficient power to separate across- and within-breed animal effects.

Conclusions

Accuracy of both single- and multi-breed genomic prediction depends on the properties of the QTL that underlie the trait. As QTL MAF decreased, accuracy decreased, especially when rare alleles had a large effect. This demonstrates that QTL properties are key parameters that determine the accuracy of genomic prediction.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-015-0124-6) contains supplementary material, which is available to authorized users.     

Photosynthetic response of Nereocystis luetkeana (Phaeophyta) to high light

Photosynthetic response to high light was determined for Bull kelp, Nereocystis luetkeana (K. Mertens) Postels and Ruprecht in order to understand how this species is affected by short‐term fluctuations in irradiance. Exposure of N. luetkeana blades to high intensity photosynthetically active radiation (1000 µmol photons m^?2 s^–1) caused increased non‐photochemical quenching of fluorescence and higher de‐epoxidation ratios for xanthophyll pigments indicating that energy‐quenching xanthophylls were used to protect blades against photoinhibition. Despite initiation of these photoprotective mechanisms, maximum photochemical efficiency of photosystem II (F_v/F_m) decreased 40% in response to a 60 min exposure to 1000 µmol photons m^?2 s^–1 photosynthetically active radiation indicating that photoinhibition had occurred. Light‐saturated rates of oxygen evolution were not changed significantly by the high light treatment. Recovery of maximum photochemical efficiency of photosystem II to within 8% of initial values occurred after a 300‐min dim light period. Younger sections of the blades were slightly more susceptible to high light damage than older sections. Middle sections of the blades were more prone to light‐induced damage at water temperatures of 7°C or 18°C, as compared to 13°C. Exposure to biologically effective ultraviolet‐B radiation (UV‐B_be) (up to 4.5 kJ m^–2 day^–1) in photoinhibitory light conditions did not significantly affect light‐induced damage to photosystem II.     

Identification of DNA repair gene Ercc1 as a novel target in melanoma

Increased expression of DNA repair genes contributes to the extreme resistance shown by melanoma to conventional DNA-damaging chemotherapeutics. One such chemotherapeutic effective against a range of other cancers, but not melanoma, is cisplatin. The DNA repair protein, ERCC1, is needed to remove cisplatin-induced DNA damage. We have shown that ERCC1 is essential for melanoma growth and resistance to cisplatin in a mouse xenograft model. Untreated xenografts of our transformed Ercc1-proficient melanocyte cell line grew very rapidly as malignant melanoma. Cisplatin treatment caused initial shrinkage of xenografts, but cisplatin-resistant regrowth soon followed. Cells reisolated into culture had twofold elevated levels of ERCC1 compared to both input cells and cells reisolated from untreated xenografts. An isogenic Ercc1-deficient derivative grew equally well in vitro as the Ercc1-proficient melanocyte cell line. However, in xenografts, the Ercc1-deficient melanomas were much slower to establish and were completely cured by just two cisplatin treatments.     

The roles of the alternative NADH dehydrogenases during oxidative stress in cultures of the filamentous fungus Aspergillus niger

Despite the importance of filamentous fungi in the biotechnology industry, little is known about their metabolism under the stressful conditions experienced in typical production fermenters. In the present study, oxygen enrichment was used to recreate an industrial batch process, and the effects of the increasing dissolved oxygen tension were studied as regards the cellular metabolism. It was found that elevated dissolved oxygen tension led to an oxidatively stressful environment, as detailed by rapid initial increases in reactive oxygen species (ROS) concentrations and antioxidant enzyme activities. Intracellular protein concentrations also decreased in oxygenated cultures; this appeared to be concomitant with a decrease in the adenosine-5'-triphosphate (ATP) pool in these cultures. Oxygenated cultures showed early senescence and death compared to aerated control cultures. Despite earlier studies proposing various mechanisms for such findings in fungal cultures subjected to oxidative stress, these findings can best be explained by the fact that in such cultures the activity of alternative NADH dehydrogenases was significantly increased, which served to maintain lower ROS concentrations throughout the duration of the process but in doing so also reduced the ability of the organism to create a proton motive force by which to drive ATP synthesis. The findings of the present study help further our understanding of the central roles of these highly conserved enzymes within fungal metabolism under oxidative stress.     

An electrochemical sensor array system for the direct, simultaneous in vitro monitoring of nitric oxide and superoxide production by cultured cells

A new approach for an amperometric array sensor platform employing arrays of sensors in a 24-well cell culture plate format has been developed for simultaneous in vitro determination of nitric oxide (NO) and superoxide free radicals (O(2)(-)) produced by stimulated cells. The work reported focuses on the direct, real-time monitoring of extracellular production of these two analytes, as well as the effects of their interaction. The sensor platform was manufactured by a combination of sputtering gold electrodes and screen-printing carbon electrodes. The O(2)(-) sensor uses covalent immobilization of cytochrome c via a binder, DTSSP (3,3'-dithio-bis(sulphosuccinimidylpropionate) onto the surface of the Au electrodes, whereas the NO sensor system involves an NiTSPc (nickel tetrasulfonated phthalocyanine) film electrodeposited onto the surface of the carbon electrodes and subsequently covered with an external layer of Nafion. For in vitro demonstration of the platforms as a potential drug-screening system, A172 glioblastoma cells were cultured and transferred into the 24-well arrays. Simultaneous and direct monitoring of NO and O(2)(-) production as a response to chemicals of biomedical relevance was carried out. The results obtained demonstrated that it would be possible to envisage a drug screening platform for compounds designed to be inhibitors of nitric oxide synthase or to have an inhibitory effect on superoxide free radical production. By suitable modification of the electrodes employed it would also be possible to extend the platform to measure alternative species.