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A C Barnes

Publications and source records attributed to A C Barnes.

At least 19 recordsLinked to original sources
PubMed2006

X-ray and neutron scattering studies of the hydration structure of alkali ions in concentrated aqueous solutions.

The presence of ions in water provides a rich and varied environment in which many natural processes occur with important consequences in biology, geology and chemistry. This article will focus on the structural properties of ions in water and it will be shown how the 'difference' methods of neutron diffraction with isotopic substitution (NDIS) and anomalous X-ray diffraction (AXD) can be used to obtain direct information regarding the radial pair distribution functions of many cations and anions in solution. This information can subsequently be used to calculate coordination numbers and to determine ion-water conformation in great detail. As well as enabling comparisons to be made amongst ions in particular groups in the periodic table, such information can also be contrasted with results provided by molecular dynamics (MD) simulation techniques. To illustrate the power of these 'difference' methods, reference will be made to the alkali group of ions, all of which have been successfully investigated by the above methods, with the exception of the radioactive element francium. Additional comments will be made on how NDIS measurements are currently being combined with MD simulations to determine the structure around complex ions and molecules, many of which are common in biological systems.

Ions↗
PubMed2005

An anomalous x-ray diffraction study of the hydration structures of Cs+ and I- in concentrated solutions.

Anomalous x-ray diffraction experiments were carried out on concentrated aqueous solutions of sodium iodide (6 molal) and cesium iodide (3 molal). Data were gathered at two energies below the absorption edges of the Cs+ and I- ions in order to avoid contributions from fluorescence. The statistics and quality of the raw data were improved by the use of a focusing analyzer crystal. Differences were taken between the data sets and used to calculate the hydration structures of Cs+ and I-. The structures found are more complex than anticipated for such large ions with relatively low charge densities and show evidence of ion-pair formation in both solutions. A two-Gaussian fit to the Cs+ data gives information about the Cs+-O and Cs+-I- correlations. The central position of the Gaussian representing the Cs+-O was fixed at 3.00 A, that is, the maximum of this contribution. The other parameters were allowed to vary freely, giving a Cs+-I- distance of 3.84+/-0.05 A and coordination numbers of 7.9 and 2.7, respectively, for the Cs+-O and Cs+-I- correlations. The results on the structure of I- in the 6 molal NaI aqueous solution were also fitted to a model based on Gaussians; this gives correlations for I- -O and I- -Na+ at 3.17+/-0.06 and 3.76+/-0.06 A with respective coordination numbers of 8.8 and 1.6. The structure of I- in the 3 molal CsI solution shows overlapping contributions due to I- -H, I- -O, and I- -Cs+. The best Gaussian fit gives two peaks centered at 3.00+/-0.08 and 3.82+/-0.04 A and shows that the latter two correlations are unresolved. The hydration structures are compared with those of other alkali and halide ions. The results are also found to be in good agreement with those obtained from standard x-ray diffraction and computer simulation.

Cesium↗
PubMed2005

Iron acquisition mechanisms of Flavobacterium psychrophilum.

Forty strains of Flavobacterium psychrophilum were tested for the production of siderophores using the universal Chrome Azurol S (CAS) assay. The majority of the strains (85%) were CAS positive (CAS+) and some (15%) were CAS negative (CAS-). The cryptic plasmid pCP1 was carried by all positive strains and was lacking from negative strains. While a weak catechol reaction was detectable in CAS+ culture supernatants, the CAS reaction was, to some extent, heat sensitive, questioning whether the positive reaction was caused only by siderophores. The ability to grow in vitro under iron-restricted conditions did not correlate with the CAS reactivity, as growth of both CAS+ and CAS- strains was similarly impaired under iron restriction induced by 2,2 dipyridyl. Suppressed growth under these conditions was restored by addition of FeCl3, haemoglobin and transferrin for both CAS+ and CAS- strains.

2,2'-Dipyridyl↗
PubMed2005

Update on bacterial vaccines: Photobacterium damselae subsp. piscicida.

Photobacterium damselae subsp. piscicida is the causative agent of pasteurellosis in wild and farmed marine fish worldwide. Although serologically homogeneous, recent molecular advances have led to the discovery of distinct genetic clades, depending on geographical origin. Further details of the strategies for host colonisation have arisen including information on the role of capsule, susceptibility to oxidative stress, confirmation of intracellular survival in host epithelial cells, and induced apoptosis of host macrophages. This improved understanding has given rise to new ideas and advances in vaccine technologies, which are reviewed in this paper.

Animals↗
PubMed2003

The hydration structure of guanidinium and thiocyanate ions: implications for protein stability in aqueous solution.

Neutron diffraction experiments were carried out on aqueous solutions containing either guanidinium or thiocyanate ions. The first-order difference method of neutron diffraction and isotopic substitution was applied, and the hydration structures of two of nature's strongest denaturant ions were determined. Each ion is shown to interact weakly with water: Guanidinium has no recognizable hydration shell and is one of the most weakly hydrated cations yet characterized. Hydration of thiocyanate is characterized by a low coordination number involving around one hydrogen-bonded water molecule and approximately two water molecules weakly interacting through "hydration bonds." The weak hydration of these denaturant ions strongly supports suggestions that a major contribution to the denaturant effect is the preferential interaction of the denaturant with the protein surface. By contrast, solute species such as many sugars and related polyols that stabilize proteins are strongly hydrated and are thus preferentially retained in the bulk solvent and excluded from the protein surface.

Biophysical Phenomena↗
PubMed2001

The gill is a major organ for antibody secreting cell production following direct immersion of sea bass (Dicentrarchus labrax, L.) in a Photobacterium damselae ssp. piscicida bacterin: an ontogenetic study.

Extremely high numbers of antibody secreting cells (ASC) were observed in the gills of sea bass fry immunised at three different age/sizes (initial weight of 0.1, 2 and 5 g) by direct immersion in a Photobacterium damselae spp. piscicida bacterin. The relatively low ASC production in the head kidney and spleen suggests that the systemic compartment was only slightly stimulated upon immersion vaccination. There was no response of corresponding magnitude in the gut as the one observed in the gills. A clear age effect was observed in the ASC response of the different groups, especially visible in the gills. Significantly higher numbers of specific ASC were observed in the gills of the two oldest groups (initial weight of 2 and 5 g) compared with the youngest fish (initial weight of 0.1 g), but the oldest groups were not significantly different from each other. Additionally, a more rapid response was observed with the ageing of the fish, with peak responses in all the organs at day 18, 16 and 8 post-immunisation in the smallest to largest fish, respectively. There was no evidence that direct immersion exposure to P. damselae ssp. piscicida at the earliest stages used in the present study (0.1 g) was tolerogenic. In the context of present knowledge, this study strongly supports the importance of the route of immunisation to locally stimulate ASC and the importance that the gills might have in specific responses.

Age Factors↗
PubMed2001

Kinetics of juvenile sea bass (Dicentrarchus labrax, L.) systemic and mucosal antibody secreting cell response to different antigens (Photobacterium damselae spp. piscicida, Vibrio anguillarum and DNP).

The ELISPOT assay was used to measure the number of specific antibody secreting cells (ASC) induced during the primary and secondary immune responses in the spleen, head kidney and gut of juvenile (5 g) sea bass (Dicentrarchus labrax) to bacterial (Vibrio anguillarum and Photobacterium damselae ssp. piscicida) and hapten dinitrophenyl-conjugated to keyhole limpet haemocyanin (DNP-KLH) antigens administered intraperitoneally. High variability among individuals was observed at each sampling day. All fish were bath vaccinated to V. anguillarum at an earlier stage (2 g) in the farm of origin prior to the development of the experiments, and therefore only secondary and tertiary responses were measured in the group immunised with this bacterium. Significant differences to the controls were observed in the primary responses of the head kidney and the spleen to P. damselae ssp. piscicida and DNP, respectively. Frequency analysis of the production of ASC suggests that significant responses in the gut might be masked by the high error variance. The peak of the primary response was observed 4 days earlier to DNP (18-20 days post-immunisation) and it was significantly higher than the response to P. damselae ssp. piscicida. Higher numbers of ASC were observed in the secondary responses of the head kidney and spleen, although they were not statistically significantly different from the primary levels, probably due to the high error variance as supported by the frequency analysis. Nevertheless, together with a faster response (peak at 7 days post-immunisation), the data suggest that memory formation had occurred. Additionally, the data suggest that some suppression of the secondary immune response in the gut might have occurred. The head kidney appears to produce the highest number of specific ASC of the organs tested. It appears that sea bass show a relatively fast but short duration antibody response.

Animals↗
PubMed1999

Peroxide-inducible catalase in Aeromonas salmonicida subsp. salmonicida protects against exogenous hydrogen peroxide and killing by activated rainbow trout, Oncorhynchus mykiss L., macrophages.

Aeromonas salmonicida subsp. salmonicida expresses a single cytoplasmically located catalase which was found to be inducible by exposure to 20 microM hydrogen peroxide in mid-exponential phase resulting in a 4 fold increase in activity. Subsequent exposure to 2 mM peroxide in late-exponential/early-stationary phase resulted in further induction of catalase activity which increased to 20 fold higher levels than those found in uninduced cultures. Exponentially induced cultures were protected against subsequent exposure to 10 mM peroxide which was lethal to non-induced cultures. Bacteria subjected to induction in mid-exponential and early-stationary phase were resistant to 100 mM peroxide, although viability was greatly reduced. Growth of the bacterium under iron-restricted conditions had no effect on the peroxide induction of catalase. As current evidence indicates, the latter is an iron-co-factored heme catalase, this result suggests that catalase induction has a high priority in the metabolism of iron. Furthermore, exposure to peroxide also induces expression of periplasmic MnSOD. A. salmonicida MT423 was resistant to normal rainbow trout macrophages, but was susceptible to killing by activated macrophages. However, if catalase was induced by prior exposure to 20 microM peroxide during mid-exponential phase, A. salmonicida was resistant to killing by activated macrophages. The ability of A. salmonicida to upregulate periplasmic MnSOD and cytoplasmic catalase production under iron restricted conditions and low level peroxide (conditions expected to exist during the early stages of an infection) may be vital for its ability to withstand attack by phagocytic cells in vivo.

Aeromonas↗
PubMed1999

Human vs robotic organ retraction during laparoscopic Nissen fundoplication.

BACKGROUND: Advances in technique and instrumentation have enabled surgeons to perform an increasing number of complicated procedures through laparoscopy. However, these efforts have often been compromised by the exertion of excessive force when anatomical structures are retracted to create a clear view of the anatomy. Here, we present a comparative study of human and robotic performance in force-controlled organ retraction during laparoscopic Nissen fundoplication (LNF). METHODS: Six female pigs (20-25 kg) were anesthetized, intubated, and placed on mechanical ventilation; pneumoperitoneum (13 mmHg CO2) was established. A force-sensing retractor (FSR) was constructed to record the forces applied in retracting the stomach during dissection of the esophageal hiatus. The FSR was calibrated using known forces and then operated by either human alone or robot under human guidance using the FSR data. The esophageal hiatus was visualized and dissected, and LNF was completed. RESULTS: Less force was needed for robotic (74.3 +/- 10.5 g; mean +/- standard deviation) than for human (108.9 +/- 34.3 g) retraction (p = 0.007) to obtain an optimal view of the esophageal hiatus. No significant differences were observed for retraction setup time (robot, 14.3 +/- 0.8 min; human, 13.7 +/- 9.9 min; mean +/- SD) or hiatal dissection time (robot, 14.0 +/- 3.0 min; human, 14.0 +/- 6.1 min; mean +/- SD). CONCLUSIONS: These preliminary results illustrate our continuing effort to develop and evaluate an automated surgical assistant for laparoscopy. As more personnel-intensive advanced laparoscopic procedures are performed, robotic retraction is likely to offer a superior alternative to human retraction; it minimizes the forces exerted on the organs while maintaining excellent anatomical view.

Animals↗
PubMed1997

A robotic system for percutaneous renal access.

PURPOSE: Percutaneous renal access can be challenging, particularly when the collecting system is not distended. Precise entry into a selected calyx facilitates subsequent percutaneous manipulations, but this skill requires extensive experience. In an attempt to improve accuracy while decreasing technical challenges, we developed a robotic system that automates the task of fluoroscopic image-guided percutaneous needle placement. MATERIALS AND METHODS: The prototype system consisted of a three degree-of-freedom robot with a needle injector end-effector. Imaging was provided by a biplanar fluoroscope. After correction of image distortion and fluoroscope calibration, robot to image-space registration was completed. To validate the system's ability to insert a needle into a calyx, ex vivo porcine kidneys suspended in agarose gel and distended with iodinated contrast solution were used as a model. In situ renal access tests with three 20 kg. pigs were performed. Access was confirmed by passing a flexible wire or aspirating iodinated contrast from the collecting system. RESULTS: The diameter of target calyces ranged from 3 to 7 mm. The in vitro accuracy of final needle tip positioning was 0.43 mm. In the ex vivo model, successful "one stick" access occurred on 10 of 12 attempts (83%). In situ access on the first attempt was successful for 6 of 12 target calyces (50%). Needle or tissue deflection accounted for each failure. CONCLUSION: The feasibility of a robotic system to assist in the percutaneous access of small and delicate renal calyces has been demonstrated. Additional work in reducing procedural steps and correcting for tissue deflection during needle passage is necessary to improve accuracy and to allow for clinical application.

Animals↗
PubMed1991

In vitro susceptibility of the fish pathogen Aeromonas salmonicida to flumequine.

The activity of the fluoroquinolone flumequine was investigated against the fish pathogen Aeromonas salmonicida and was compared with that of oxolinic acid. Flumequine was more active than oxolinic acid in terms of its MIC against oxolinic acid-resistant isolates of A. salmonicida and was as active as oxolinic acid against susceptible isolates. In contrast to oxolinic acid, flumequine was bactericidal, with only 1% of the bacteria surviving 6 h of exposure to the drug at concentrations slightly above the MIC. Mutation to resistance to flumequine was found to occur at a lower frequency than that to oxolinic acid. Hence, in vitro, flumequine appears to possess some advantages over oxolinic acid against this fish pathogen.

Aeromonas↗
PubMed1990

Cross resistance between oxytetracycline and oxolinic acid in Aeromonas salmonicida associated with alterations in outer membrane proteins.

Oxytetracycline resistant mutants of Aeromonas salmonicida isolated from mutation frequency experiments showed decreased susceptibility to oxolinic acid. Outer membrane preparations of these resistant mutant strains revealed a major protein, with a molecular mass of approximately 37 kDa, which was not present in significant quantities in the parent strain.

Aeromonas↗
PubMed1990

In vitro activities of 4-quinolones against the fish pathogen Aeromonas salmonicida.

The activities of five fluorinated 4-quinolones, namely, sarafloxacin, enrofloxacin, PD127391, PD117596, and CI934, against the fish pathogen Aeromonas salmonicida were investigated and compared with that of oxolinic acid. The results indicated that with the exception of CI934, these drugs are more active than oxolinic acid in terms of MIC. No inoculum effect was observed, but the drugs were less active at 10 degrees C than at 22 degrees C. The presence of 3% of NaCl caused an increase in drug activity. Resistance to the drugs appeared to be fairly stable, with only a small decrease in activity after 10 successive passages of the test strains on drug-free tryptone soya agar.

Aeromonas↗
PubMed1988

Synthesis and oral antiallergic activity of carboxylic acids derived from imidazo[2,1-c][1,4]benzoxazines, imidazo[1,2-a]quinolines, imidazo[1,2-a]quinoxalines, imidazo[1,2-a]quinoxalinones, pyrrolo[1,2-a]quinoxalinones, pyrrolo[2,3-a]quinoxalinones, and imidazo[2,1-b]benzothiazoles.

4H-Imidazo[2,1-c][1,4]benzoxazine-2-carboxylic acid (3) was found to possess potent activity in the IgE-induced rat passive cutaneous anaphylaxis model which may be predictive of clinical antiallergic activity. Compared to disodium cromoglycate (DSCG, 1), 3 was less active following iv administration but unlike DSCG showed very significant oral activity. To explore the structural requirements for this activity, a range of tricyclic compounds was prepared and their activities were measured. Individual 2-carboxylic acids derived from imidazo[1,2-a]quinolines, imidazo[1,2-a]quinoxalines, imidazo[1,2-a]quinoxalinones, pyrrolo[1,2-a]quinoxalinones, pyrrolo[2,3-a]quinoxalinones, and imidazo[2,1-b]benzothiazoles showed iv activities up to 10(3) times as potent as DSCG and many of them showed significant oral activity. From these, imidazo[1,2-a]quinoxaline-2-carboxylic acid 114 has been chosen for further development.

Animals↗
PubMed1979

Pharmacologically active sulfoximides: 5-hexyl-7-)S-methylsulfonimidoly) xanthone-2-carboxylic acid, a potent antiallergic agent.

The antiallergic activity of some xanthone derivatives containing a sulfoximide substitutent has been investigated. While 2-(S-methylsulfonimidoyl)xanthone itself was found to be inactive, a series of 7-(S-methylsulfonimidoly)-xanthone-2-carboxylic acids showed good levels of activity in the passive cutaneous anaphylaxis screen. N-Substituted sulfoximide derivatives were, without exception, less active than the corresponding unsubstituted compounds. The activity of the 7-(S-methylsulfonimidoyl)xanthone-2-carboxylic acids could be enhanced by the introduction of an alkyl or alkoxy substituent at C-5. As a result of these studies, 5-hexyl-7(S-methylsulfonimidoyl)xanthone-2-carboxylic acid has been selected for further investigation as an antipasthmatic agent.

Animals↗