Use of the modified Robbins device to study the in vitro biofilm removal efficacy of NitrAdine, a novel disinfecting formula for the maintenance of oral medical devices

Aims:  To evaluate the use of the modified Robbins device (MRD) to test disinfection strategies against biofilms that form on oral medical devices and to test the biofilm removal efficacy of NitrAdine^TM, a disinfectant for the maintenance of oral medical devices.
Methods and Results:  Biofilms were grown on discs using the MRD and biofilms formed in this system were used to evaluate the efficacy of NitrAdine^TM and to determine the optimal disinfection conditions. Our data indicate that the use of the MRD allows for the rapid and reproducible formation of high-density biofilms. Determination of the efficacy of NitrAdine^TM revealed high activity against biofilms tested (e.g. >3 log reduction for Candida albicans and Staphylococcus aureus ) and allowed the determination of the optimal conditions for its use.
Conclusion:  The high reproducibility and flexibility of the MRD make it an excellent candidate for standardized testing of disinfectants aimed at reducing biofilms on oral medical devices. Using this system, we were able to demonstrate that NitrAdine^TM exhibits high activity against biofilms formed by the micro-organisms tested.
Significance and Impact of the Study:  Our data suggest that our procedure is appropriate for standardized testing of disinfectants aimed at reducing biofilms on oral medical devices.     

3-Hydroxypropionaldehyde guided glycerol feeding strategy in aerobic 1,3-propanediol production by <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis>

3-Hydroxypropionaldehyde (3-HPA) is a toxic intermediary metabolite in the biological route of 1,3-propanediol biosynthesis from glycerol. 3-HPA accumulated in culture medium would arouse an irreversible cessation of the fermentation process. The role of substrate (glycerol) on 3-HPA accumulation in aerobic fermentation was investigated in this paper. 1,3-Propanediol oxidoreductase and glycerol dehydratase, two key enzyme catalyzing reactions of 3-HPA formation and consumption, were sensitive to high concentration of 3-HPA. When the concentration of 3-HPA increased to a higher level in medium (ac 10 mmol/L), the activity of 1,3-propanediol oxidoreductase in cell decreased correspondingly, which led to decrease of the 3-HPA conversion rate, then the 3-HPA concentration increasing was accelerated furthermore. 3-HPA accumulation in culture medium was triggered by this positive feedback mechanism. In the cell exponential growth phase, the reaction catalyzed by 1,3-propanediol oxidoreductase was the rate limiting step in 1,3-propanediol production. The level of 3-HPA in culture medium could be controlled by the substrate (glycerol) concentration, and lower level of glycerol could avoid 3-HPA accumulating to a high, lethal concentration. In fed batch fermentation, under the condition of initial glycerol concentration 30 g/L, and keeping glycerol concentration lower than 7–8 g/L in cell exponential growth phase, 3-HPA accumulation could not be incurred. Based on this result, a glycerol feeding strategy was set up in fed batch fermentation. Under the optimized condition, 50.1 g/L of 1,3-propanediol was produced in 24 h, and 73.1 g/L of final 1,3-propanediol concentration was obtained in 54 h.     

Redox state and gender differences in vascular smooth muscle cells

Vascular smooth muscle cells (VSMC) have been isolated from male and female rat aorta and studied to assess their susceptibility to ultraviolet radiation-induced oxidative stress. Interestingly, a gender difference, in terms of reactive oxygen species production, was detected in both basal and irradiated VSMC. Namely, VSMC from male rats were more susceptible to radiation-induced stress and easier underwent apoptosis in comparison to cells from female rats. Conversely, the latter, in the same experimental conditions, clearly displayed signs of premature senescence. These results indicate that a sort of "gender memory" can be conserved in VMSC in primary culture.     

Feeding differences among common littoral mysids, <Emphasis Type="Italic">Neomysis integer,Praunus flexuosus</Emphasis> and <Emphasis Type="Italic">P. inermis</Emphasis>

The energy flow in aquatic food webs and their structures are largely determined by food utilisation of predators. Mysid shrimps are important predators in various aquatic ecosystems. We studied the stomach contents of three common littoral mysids from the Baltic Sea. The aim was to study whether the diets differ between species and size classes inhabiting shallow coastal areas. The effects of season (spring, summer, autumn) and habitat were also explored. Results showed that all species were highly omnivorous, utilising various phyto- and zooplankton prey, algal filaments and dead organic material through the growing season. No ontogenetic diet shifts were observed although different size classes preferred slightly different prey. The amount of detritus increased in the diets during growth. In addition, large mysids ate more macro- and less microzooplankton compared with the small ones. There were also species-specific differences in the food utilisation. Neomysis integer ate more benthic material, Praunus flexuosus more macrozooplankton and P. inermis more phytoplankton compared with the others. These differences reflect microhabitat differences and probably also size differences of the studied species. Seasonal variation was also observed in the diets. Food utilisation followed the changes in the food availability, e.g. phytoplankton spring bloom and zooplankton peak abundances in late summer. Results confirm the omnivorous nature of mysids showing the importance of a diversity of prey as energy sources during growth.     

Impact of weather variation on feeding behaviour, nestling growth and brood survival in Wrynecks Jynx torquilla

While habitat destruction is thought to be the most important reason for the decline of the Wryneck Jynx torquilla throughout Europe, it has been hypothesised that weather factors may also play a crucial role. We studied the impact of variations in ambient temperature and rainfall on feeding behaviour, nestling growth and daily brood survival probabilities in a population from the Swiss Alps. We recorded the frequency of food provisioning and measured nestlings’ growth on 6 days at 17 nests, and monitored the success of 181 broods from 2002 to 2006. The mean feeding frequency was 7.9 feedings per hour, and increased with temperature and with nestling age. Changes of body mass, tarsus length and of the 8th primary feather were not strongly influenced by temperature and rainfall. Body growth was negatively influenced by the initial size of the different body measures towards the end of the growing phase of the corresponding body measure, pointing towards compensatory growth. Daily brood survival probabilities declined in the course of the season and with increasing rainfall, and they increased with increasing temperature and with increasing nestling age. Our findings highlight that the effects of adverse weather on feeding behaviour, nestling growth and nest survival in Wrynecks are complex, as they alter with the age of the nestlings and possibly with the duration of the adverse weather events. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

A Novel Device for the Collection, Storage, Transport, and Delivery of Beneficial Insects, and its Application to Ophraella communa (Coleoptera: Chrysomelidae)

A multi-use device was developed for the collection, short-term storage, transport, and delivery of Ophraella communa (Coleoptera: Chrysomelidae), a biological control agent of common ragweed, Ambrosia artemisiifolia. The device is made from a 125-ml plastic specimen container that can hold O. communa adults or pupae. When used as an aspirator, insect collection and counting times are reduced. O. communa adults and pupae can be stored inside the container at 3°C with median survival of 41 and 21 days, respectively. A cotton wick saturated with water or a 5% sugar solution nourishes insects during transport and the container design minimizes insect mortality by providing an optimum microclimate during insect storage and transport. Designed to protect insects from rainfall and to limit encounters with predators and parasites, the containers can be used for field releases of O. communa adults and pupae. Although the container has been designed and tested for O. communa, it is highly versatile and could possibly be used with a variety of insect species.     

Effect of the degree of autotomy on feeding, growth, and reproductive capacity in the multi-armed sea star Heliaster helianthus

The term autotomy refers to the process by which some species lose limbs or parts of limbs in response to adverse biotic or abiotic conditions, as for example, predation or abnormally high temperatures. The multi-armed sea star Heliaster helianthus is a key predator of the intertidal and the shallow rocky subtidal communities of north-central Chile. Natural populations of this sea star have been found with up to 60% of the individuals showing some degree of autotomy. The present study evaluated the effects of autotomy on feeding rate and growth of juvenile and adult H. helianthus after experimentally induced autotomy of 17% and 33% of their arms, as well as on the energy content of the pyloric caeca and gonads of adults during the reproductive period. Experimental juvenile sea stars were maintained and fed in the laboratory over a period of five months and adult sea stars for one month, Intact individuals were maintained as parallel controls. The results showed that juveniles undergoing 33% autotomy decreased their feeding rates, and as a consequence showed lowered net individual growth. In contrast, adults with 17% and 33% autotomy showed marked reductions in feeding. The results showed that autotomized adults had between five and seven times lower contents of carbohydrates, lipids, and proteins (and thus energetic content) in their pyloric caeca and gonads. The loss of the arms not only decreased the capacity for feeding in sea stars, but also allocated energy away from growth and reproduction into the process of regeneration of arms. This suggests that autotomy reduces the fitness of H. helianthus. Growth was reduced in the juveniles, while adults became limited in their ability to store energy which then limited their reproductive potential. Finally, based on the important effect of autotomy on reducing the feeding capacity of H. helianthus, the role of this sea star as a predator in the environment may be strongly affected.     

DNA as a ‘Nanomaterial’

DNA is recognized as a nanomaterial, not as a biological material, in the research field of nanotechnology. This article reviews recent research on nanowires, nanoarchitectures, computing, aptamers, biocatalysts, devices, and machines using DNA. In these works, the characteristics of DNA including facile synthesis by the solid-phase method, self-assembly, electro-conductivity, information elements, amplification, switching, molecular recognition, and catalytic functions, were appropriately applied. Multiple functions of DNA could be used simultaneously, and activated independently, by molecular switching. Therefore, the combinations of functional sequences of DNA can produce unique materials. It is obvious that the DNA molecule is one of the most promising functional nanomaterials. However, the application of DNA molecules is still under study because of the big gap that exists between theory and practice. We eagerly anticipate a ‘coming out’ of DNA due to breakthroughs in nanobiotechnology.     

Correlations of cibarial muscle activities of Homalodisca spp. sharpshooters (Hemiptera: Cicadellidae) with EPG ingestion waveform and excretion

Fluid flow into and out of the stylets of xylem-ingesting sharpshooters (Hemiptera: Cicadellidae: Cicadellinae) is powered by muscles of the cibarial pump. Such fluid flow is crucial for transmission of Xylella fastidiosa, the Pierce’s Disease bacterium, yet has not been rigorously studied via electrical penetration graph (EPG) technology. We correlated EPG waveforms with electromyographically (EMG) recorded muscle potentials from the cibarial dilator muscles, which power the piston-like cibarial diaphragm. There was a 1:1 correspondence of each cycle of cibarial muscle contraction/relaxation with each plateau of EPG waveform C. Results definitively showed that the C waveform represents active ingestion, i.e. fluid flow is propelled by cibarial muscle contraction. Moreover, each C waveform episode represents muscular diaphragm uplift, probably combined with a “bounce” from cuticular elasticity, to provide the suction that pulls fluid into the stylets. Fine structure of the EPG ingestion waveform represents directionality of fluid flow, supporting the primary role of streaming potentials as the electrical origin of the C waveform. Rhythmic bouts of cibarial pumping were generally correlated with sustained production of excretory droplets. However, neither the onset nor cessation of ingestion was correlated with onset or cessation of excretion, respectively. Volume of excreta is an inexact measure of ingestion. Implications for using EPG to understand the mechanism of X. fastidiosa transmission are discussed.     

Prey capture and accommodation in the sandlance, Limnichthyes fasciatus (Creediidae; Teleostei)

The eyes of the sandlance, Limnichthyes fasciatus (Creediidae, Teleostei) move independently and possess a refractive cornea, a convexiclivate fovea and a non-spherical lens giving rise to a wide separation of the nodal point from the axis of rotation of the eye much like that of a chameleon. To investigate this apparent convergence of the visual optics in these phylogenetically disparate species, we examine feeding behaviour and accommodation in the sandlance with special reference to the possibility that sandlances use accommodation as a depth cue to judge strike length. Frame-by-frame analysis of over 2000 strikes show a 100% success rate. Explosive strikes are completed in 50 ms over prey distances of four body lengths. Close-up video confirms that successful strikes can be initiated monocularly (both normally and after monocular occlusion) showing that binocular cues are not necessary to judge the length of a strike. Additional means of judging prey distance may also be derived from parallax information generated by rotation of the eye as suggested for chameleons. Using photorefraction on anaesthetised sandlances, accommodative changes were induced with acetylcholine and found to range between 120 D and 180 D at a speed of 600–720 D s⁻¹. The large range of accommodation (25% of the total power) is also thought to be mediated by corneal accommodation where the contraction of a unique cornealis muscle acts to change the corneal curvatures. Accepted: 8 December 1999