A tool for live-cell confocal imaging of temperature-dependent organelle dynamics

Intracellular organelles alter their morphology in response to ambient conditions such as temperature to optimize physiological activities in cells. Observing organelle dynamics at various temperatures deepens our understanding of cellular responses to the environment. Confocal laser microscopy is a powerful tool for live-cell imaging of fluorescently labeled organelles. However, the large contact area between the specimen and the ambient air on the microscope stage makes it difficult to maintain accurate cellular temperatures. Here, we present a method for precisely controlling cellular temperatures using a custom-made adaptor that can be installed on a commercially available temperature-controlled microscope stage. Using this adaptor, we observed temperature-dependent organelle dynamics in living plant cells; morphological changes in chloroplasts and peroxisomes were temperature dependent. This newly developed adaptor can easily be placed on a temperature-controlled stage to capture intracellular responses to temperature at unprecedentedly high resolution.

Epimorphic development in tropical shallow-water Nymphonidae (Arthropoda: Pycnogonida) revealed by fluorescence imaging

BACKGROUND

Extant lineages of sea spiders (Pycnogonida) exhibit different types of development. Most commonly, pycnogonids hatch as a minute, feeding protonymphon larva with subsequent anamorphic development. However, especially in cold water habitats at higher latitudes and in the deep sea, some taxa have large, lecithotrophic larvae, or even undergo extended embryonic development with significantly advanced postlarval hatching stages. Similar biogeographic trends are observed in other marine invertebrates, often referred to as "Thorson's rule".

RESULTS

To expand our knowledge on the developmental diversity in the most speciose pycnogonid genus Nymphon, we studied the developmental stages of the two tropical representatives N. floridanum and N. micronesicum., We compared classical scanning electron microscopy with fluorescence-based approaches to determine which imaging strategy is better suited for the ethanol-fixed material available. Both species show epimorphic development and hatch as an advanced, lecithotrophic postlarval instar possessing the anlagen of all body segments. Leg pairs 1-3 show a considerable degree of differentiation at hatching, but their proximal regions remain coiled and hidden under the cuticle of the hatching instar. The adult palp and oviger are not anteceded by three-articled larval limbs, but differentiate directly from non-articulated limb buds during postembryonic development.

CONCLUSIONS

Fluorescence imaging yielded more reliable morphological data than classical scanning electron microscopy, being the method of choice for maximal information gain from rare and fragile sea spider samples fixed in high-percentage ethanol. The discovery of epimorphic development with lecithotrophic postlarval instars in two small Nymphon species from tropical shallow-water habitats challenges the notion that this developmental pathway represents an exclusive cold-water adaptation in Nymphonidae. Instead, close phylogenetic affinities to the likewise more direct-developing Callipallenidae hint at a common evolutionary origin of this trait in the clade Nymphonoidea (Callipallenidae + Nymphonidae). The lack of functional palpal and ovigeral larval limbs in callipallenids and postlarval hatchers among nymphonids may be a derived character of Nymphonoidea. To further test this hypothesis, a stable and well-resolved phylogenetic backbone for Nymphonoidea is key.

Mass transfer of nanobubble aeration and its effect on biofilm growth: Microbial activity and structural properties

It is necessary to improve the performance and reduce the aeration cost is of wastewater treatment by aerobic biofilm systems. Nanobubble aeration is supposed to be a promising method to achieve these goals. Compared with coarse bubbles, dissolved oxygen profiling showed that the nanobubbles provided more oxygen to biofilms, offering superior oxygen supply capacity and 1.5 times higher oxygen transfer efficiency. Nanobubble aeration accelerated the growth of the biofilm and achieved better removal efficiencies of chemical oxygen demand and ammonia, with as maximum as six times higher dehydrogenase activity, and more extracellular polymeric substance content than when using the traditional aeration mode. This is attributed to the enhancement of metabolism and the proliferation of microorganisms. Confocal laser-scanning microscopy imaging confirmed that nanobubble aeration affected the components of biofilm by shifting the microbial community and changing its metabolic pathways of biofilms, such as carbohydrate synthesis. Nanobubble aeration resulted in an energy saving of approximately 80%. The assessment of nanobubble aerated biofilm growth suggests that this technique can offer a rapid-initiation, high efficiency, and low-cost strategy for aerobic biofilm systems in wastewater treatment.

Comparison of the antibacterial activity of calcium silicate- and epoxy resin-based endodontic sealers against Enterococcus faecalis biofilms: a confocal laser-scanning microscopy analysis

This study assessed the antibacterial activity of BioRoot RCS in comparison with that of the Totalfill BC and AH Plus sealers against Enterococcus faecalis biofilms in dentinal tubules using confocal laser-scanning microscopy. Sixty-six root dentin halves were prepared and sterilized. Three sections were used to ensure sterilization. The remaining were inoculated with E. faecalis. Three specimens were examined to verify the viability of biofilms. The sixty specimens were randomly divided into four groups: AH Plus, BioRoot RCS, Totalfill BC sealer, and no sealer. The specimens were incubated for 1, 7, and 30 days. The specimens were stained and four corners of each disc were scanned. Statistical analysis was performed using two-way ANOVA and Tukey's post hoc test. Almost half of the bacteria were dead in BioRoot RCS group on day 1 and in Totalfill BC group on day 7. All sealers killed significantly more bacteria than the control after 30 days (P < .05). On day 7, Totalfill BC showed a significantly higher percentage of dead bacteria than BioRoot RCS (P < .05). On day 30, the BioRoot RCS group registered the highest percentage of dead cells (61.75%), which was significantly higher than the percentages of the AH Plus and Totalfill BC groups (P < .05). Calcium silicate-based root canal sealers exerted antimicrobial effects against E. faecalis biofilms. The antibacterial activity of BioRoot RCS was significantly higher than that of the Totalfill BC and AH Plus sealers after 30 days of exposure.

The neuroanatomy of Barentsia discreta (Entoprocta, Coloniales) reveals significant differences between bryozoan and entoproct nervous systems

BACKGROUND

Entoprocta affinities within Lophotrochozoa remain unclear. In different studies, entoprocts are considered to be related to different groups, including Cycliophora, Bryozoa, Annelida, and Mollusca. The use of modern methods to study the neuroanatomy of Entoprocta should provide new information that may be useful for phylogenetic analysis.

RESULTS

The anatomy of the nervous system in the colonial Barentsia discreta was studied using immunocytochemistry and transmission electron microscopy. The ganglion gives rise to several main nerves: paired lateral, aboral, and arcuate nerves, and three pairs of tentacular cords that branch out into tentacular nerves. The serotonergic nervous system includes paired esophageal perikarya and two large peripheral perikarya, each with a complex net of neurites. Each tentacle is innervated by one abfrontal and two laterofrontal neurite bundles. Sensory cells occur regularly along the abfrontal side of each tentacle. Star-like nerve cells are scattered in the epidermis of the calyx. The stalk is innervated by paired stalk nerves.

CONCLUSIONS

The neuroanatomy of the colonial Barentsia discreta is generally similar to that of solitary entoprocts but differs in the anatomy and ultrastructure of the ganglion, the number of neurite bundles in the calyx, and the distribution of serotonin in the nerve elements. A comparison of the organization of the nervous system in the Entoprocta and Bryozoa reveals many differences in tentacle innervations, which may indicate that these groups may not be closely related. Our results can not support with any certainty the homology of nervous system elements in adult entoprocts and adult "basal mollusks".

Proteo-lipobeads to encapsulate cytochrome c oxidase from Paracoccus denitrificans

Proteo-lipobeads (PLBs) are investigated as cell-free model systems to encapsulate membrane proteins such as ion channels and transporters. PLBs are based on nickel nitrile tri-acetic acid (Ni-NTA)-functionalized agarose beads, onto which membrane proteins (MP) are bound via histidine(his)-tag. Composite beads thus obtained (subsequently called proteobeads) are dialyzed in the presence of lipid micelles to form PLBs. As an example we employed cytochrome c oxidase from P. denitrificans with a his-tag fused to the C-terminus of subunitI. In this orientation the P side of CcO faces the outside of the PLB and hence protons are released to the outer aqueous phase, when electron transfer is initiated by light excitation of Ru complexes. Proton release kinetics was probed by fluorescence microscopy using the pH-sensitive sensor molecule fluorescein DHPE inserted into the lipid layer. In order to monitor the generation of membrane potentials we performed a FLIPR assay on the CcO embedded in PLBs using the FRET pair CC2-DMPE/DiSBAC2(3). The combined results show that PLBs can be used as a model system designed to quantify the kinetic parameters of membrane proteins. In addition, the FLIPR assay demonstrates the feasibility of PLBs for high throughput screening applications.

PNA-COMBO-FISH: From combinatorial probe design in silico to vitality compatible, specific labelling of gene targets in cell nuclei

Recently, advantages concerning targeting specificity of PCR constructed oligonucleotide FISH probes in contrast to established FISH probes, e.g. BAC clones, have been demonstrated. These techniques, however, are still using labelling protocols with DNA denaturing steps applying harsh heat treatment with or without further denaturing chemical agents. COMBO-FISH (COMBinatorial Oligonucleotide FISH) allows the design of specific oligonucleotide probe combinations in silico. Thus, being independent from primer libraries or PCR laboratory conditions, the probe sequences extracted by computer sequence data base search can also be synthesized as single stranded PNA-probes (Peptide Nucleic Acid probes) or TINA-DNA (Twisted Intercalating Nucleic Acids). Gene targets can be specifically labelled with at least about 20 probes obtaining visibly background free specimens. By using appropriately designed triplex forming oligonucleotides, the denaturing procedures can completely be omitted. These results reveal a significant step towards oligonucleotide-FISH maintaining the 3d-nanostructure and even the viability of the cell target. The method is demonstrated with the detection of Her2/neu and GRB7 genes, which are indicators in breast cancer diagnosis and therapy.

Changes in cell size and number and in rhizodermal development contribute to root tip swelling of Hyoscyamus albus roots subjected to iron deficiency

Root tip swelling is a common phenomenon observed when plant roots are subjected to Fe deficiency. We analysed whether an increase in cell number or an enlargement of cell width was involved in this phenomenon. Root tips of Hyoscyamus albus cultured with or without Fe were stained with fluorescent SYTO14 and analysed by confocal laser-scanning microscopy. Time-course and position-based examination revealed that the inhibition of longitudinal cell elongation and acceleration of transverse cell enlargement under Fe deficiency started from the tips and then extended towards the base during the time-course period. An increase in cell number also occurred behind the tips. In addition, the development of rhizodermal protrusions was observed on the surface of roots subjected to Fe deficiency. These results indicated that changes in cell size and number and in root hair development were all involved in root tip swelling.