Geometry of α-Cr2O3(0001) as a Function of H2O Partial Pressure

Surface X-ray diffraction has been employed to elucidate the surface structure of α-Cr₂O₃(0001) as a function of water partial pressure at room temperature. In ultra high vacuum, following exposure to ∼2000 Langmuir of H₂O, the surface is found to be terminated by a partially occupied double layer of chromium atoms. No evidence of adsorbed OH/H₂O is found, which is likely due to either adsorption at minority sites, or X-ray induced desorption. At a water partial pressure of ∼30 mbar, a single OH/H₂O species is found to be bound atop each surface Cr atom. This adsorption geometry does not agree with that predicted by ab initio calculations, which may be a result of some differences between the experimental conditions and those modeled.

Controlled cobalt doping in biogenic magnetite nanoparticles

Cobalt-doped magnetite (CoxFe3 -xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe(2+) site with Co(2+), with up to 17 per cent Co substituted into tetrahedral sites.

Arsenic release and attenuation in low organic carbon aquifer sediments from West Bengal

High arsenic concentrations in groundwater are causing a humanitarian disaster in Southeast Asia. It is generally accepted that microbial activities play a critical role in the mobilization of arsenic from the sediments, with metal-reducing bacteria stimulated by organic carbon implicated. However, the detailed mechanisms underpinning these processes remain poorly understood. Of particular importance is the nature of the organic carbon driving the reduction of sorbed As(V) to the more mobile As(III), and the interplay between iron and sulphide minerals that can potentially immobilize both oxidation states of arsenic. Using a multidisciplinary approach, we identified the critical factors leading to arsenic release from West Bengal sediments. The results show that a cascade of redox processes was supported in the absence of high loadings of labile organic matter. Arsenic release was associated with As(V) and Fe(III) reduction, while the removal of arsenic was concomitant with sulphate reduction. The microbial populations potentially catalysing arsenic and sulphate reduction were identified by targeting the genes arrA and dsrB, and the total bacterial and archaeal communities by 16S rRNA gene analysis. Results suggest that very low concentrations of organic matter are able to support microbial arsenic mobilization via metal reduction, and subsequent arsenic mitigation through sulphate reduction. It may therefore be possible to enhance sulphate reduction through subtle manipulations to the carbon loading in such aquifers, to minimize the concentrations of arsenic in groundwaters.

Model system studies of the influence of bacterial biofilm formation on mineral surface reactivity

Biofilm development on mineral surfaces and related changes in surface reactivity were studied using batch and flow through experiments. An artificial groundwater was used as the primary nutrient medium, Pseudomonas aeruginosa (PAO1) was the model microbial organism and 'mineral' surfaces were kept as simple as possible by using glass or a polished quartz tile. Experiments were also completed with very low concentrations (100 mg l(-1)) of iron, Fe(2+ ), in the solution. In situ confocal laser scanning microscopy of developing colonies during the live growth phase, and of thick, mature biofilms, revealed only sporadic coverage of biofilm cells and associated polymers at the 'mineral-microbe interface'. Imaging and analysis of biofilm-conditioned surfaces doped with Fe(2+ )-rich solutions allowed the locus and form of Fe-rich mineral precipitation to be determined and show that biological surface components can cause mineral precipitation from dilute dissolved species which might otherwise remain in solution.

Biomineralization: linking the fossil record to the production of high value functional materials

The microbial cell offers a highly efficient template for the formation of nanoparticles with interesting properties including high catalytic, magnetic and light-emitting activities. Thus biomineralization products are not only important in global biogeochemical cycles, but they also have considerable commercial potential, offering new methods for material synthesis that eliminate toxic organic solvents and minimize expensive high-temperature and pressure processing steps. In this review we describe a range of bacterial processes that can be harnessed to make precious metal catalysts from waste streams, ferrite spinels for biomedicine and catalysis, metal phosphates for environmental remediation and biomedical applications, and biogenic selenides for a range of optical devices. Recent molecular-scale studies have shown that the structure and properties of bionanominerals can be fine-tuned by subtle manipulations to the starting materials and to the genetic makeup of the cell. This review is dedicated to the late Terry Beveridge who contributed much to the field of biomineralization, and provided early models to rationalize the mechanisms of biomineral synthesis, including those of geological and commercial potential.

Oxygen therapy for cystic fibrosis

BACKGROUND

The most serious complications of cystic fibrosis (CF) relate to respiratory insufficiency. Oxygen supplementation therapy has been a standard of care for individuals with chronic lung diseases associated with hypoxemia for decades. It is common for physicians to prescribe oxygen therapy for people with CF when hypoxemia occurs. However, it is unclear if empiric evidence is available to provide indications for this therapy with its financial costs and often profound impact on lifestyle.

OBJECTIVES

To assess whether oxygen therapy improves the longevity or quality of life of individuals with CF.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Most recent search of Group's Trials Register: April 2005.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials comparing oxygen, administered at any concentration, by any route, in people with documented CF for any time period.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data.

MAIN RESULTS

Nine published studies (149 participants) are included in this review, of which only one examined long-term oxygen therapy (28 participants). There was no statistically significant improvement in survival, lung, or cardiac health. Four studies examined the effect of oxygen supplementation during sleep by polysomnography. Although oxygenation improved, there were no demonstrable improvements in qualitative sleep parameters and modest hypoventilation was noted. In three studies, oxygen supplementation was evaluated during exercise. Hypoxemia was prevented, but mild hypercapnia resulted. Work performance was not improved, as measured in one study, but was improved in a second study. Furthermore, in two studies, exercise duration was enhanced by oxygen supplementation. In the study examining the impact of oxygen supplementation after exercise, recovery time was enhanced.

AUTHORS' CONCLUSIONS

There are no published data to guide the prescription of chronic oxygen supplementation to people with advanced lung disease due to CF. Short-term oxygen therapy during sleep and exercise improves oxygenation but is associated with modest and probably clinically inconsequential hypercapnia. During exercise, there are improvements in exercise duration and peak performance. There is a need for larger, well-designed clinical trials to assess the benefits of long-term oxygen therapy in people with CF administered continuously or during exercise or sleep or both.

Retained wooden foreign body in a child's thigh complicated by severe necrotizing fasciitis: a case report and discussion of imaging modalities for early diagnosis

Soft tissue foreign bodies (FB) represent a common cause for emergency department visits. Diagnosis may be difficult especially with non-radiopaque FB. The clinical course may be complicated by superficial or deep tissue infection. Use of imaging modalities such as ultrasound may be important for early diagnosis. We report a case of retained foreign body with a complicated clinical course and discuss imaging modalities that may have aided in the early diagnosis.

Choice of opioid for initiation of combined spinal epidural analgesia in labour--fentanyl or diamorphine

Sixty-two women requesting regional analgesia in labour were allocated to receive a 1.5 ml intrathecal injection as part of a combined spinal-epidural (CSE) analgesic technique. This contained either bupivacaine 2.5 mg plus fentanyl 25 microg (group F) or bupivacaine 2.5 mg plus diamorphine 250 microg (group D). Times of analgesic onset and offset were recorded, motor and proprioceptive assessments made and side-effects noted. Analgesic onset was not significantly different between the groups (group F, 8.0 min; group D, 9.5 min; P = 0.3) but time to first top-up request was significantly longer in the diamorphine group (group F, 73 min; group D, 101 min; P = 0.003). Motor loss, assessed by the modified Bromage score, was statistically but not clinically greater in the fentanyl group (P = 0.01). Maternal hypotension, pruritus, proprioceptive loss, nausea and fetal bradycardia were rare and not severe, and their incidences did not differ between groups. No respiratory depression was observed after CSE. This use of diamorphine was not associated with increased side-effects compared with fentanyl/bupivacaine, and it has a longer duration of action.

Effect of tramadol on electroencephalographic and auditory-evoked response variables during light anaesthesia

Tramadol is a centrally acting opioid-like analgesic commonly used for analgesia during surgery. It has been stated that the use of tramadol increases the risk of awareness during anaesthesia. We studied 29 patients under steady state anaesthesia, ventilated via a laryngeal mask airway with 0.6 MAC isoflurane in 50% nitrous oxide, and with no surgical stimulus. The electroencephalogram (EEG) and auditory-evoked response (AER) were recorded throughout the study period, as were pulse and arterial pressure. Patients were given randomly a bolus of either saline (S), tramadol 100 mg (T1), or tramadol 200 mg (T2). Significant increases in systolic arterial pressure and decreases in heart rate were seen in the tramadol groups compared to the saline group. Significant, dose-related activation in all EEG variables (median power frequency, spectral edge, Delta Power and Alpha/Delta ratio) but no significant change in Pa or Nb amplitudes or latencies were noted. The EEG changes were not at levels thought to be associated with awareness. This study indicates that tramadol, whilst causing EEG activation, has no effect on depth of anaesthesia as measured by the AER.

Cranial subdural haematoma associated with dural puncture in labour

A 23-yr-old primagravida sustained a dural puncture during epidural catheter insertion and developed a headache that settled with oral diclofenac and codydramol. On the third day after delivery, she convulsed twice without warning. As plasma urate was increased, the putative diagnosis of an eclamptic fit was made, and magnesium therapy was started. A contrast CT scan revealed that the cause of the patient's symptoms was a subdural haematoma with raised intracranial pressure. A coincidental arteriovenous malformation was noted. This case emphasises the need to consider the differential diagnoses of post-partum headache. The management of acute intracranial haematoma is described.

Speed of onset of regional analgesia in labour: a comparison of the epidural and spinal routes

This study compares the speed of onset of effective analgesia in two randomly assigned groups of patients requesting analgesia in labour. Patients in the combined spinal-epidural group (n = 69) were given a subarachnoid injection of 1.5 ml containing bupivacaine 2.5 mg and fentanyl 25 microg for initiation of analgesia. Patients in the epidural group (n = 73) were given an epidural injection of 10 ml containing bupivacaine 12.5 mg and fentanyl 50 microg. Mean (SD) onset times to the first pain-free contraction were 10.0 (5.7) min in the combined spinal-epidural group and 12.1 (6.5) min in the epidural group (p = 0.054). Patients in the combined spinal-epidural group suffered a higher incidence of motor weakness and proprioceptive deficit than those in the epidural group (p = 0.01). The incidence of technique failure and side-effects was similar in the two groups. It is our contention that the statistically nonsignificant difference in onset times does not justify the additional potential for side-effects and the extra cost of the equipment involved in the combined spinal-epidural technique.

Rotating Ring (Pt)-Disc (FeS2) Electrode Behavior in Hydrochloric Solutions

A rotating ring (Pt)-disc (FeS2) electrode was used to investigate the surface oxidation process of pyrite in the hydrochloric solutions. It is reported for the first time that the oxidation intermediates of pyrite were formed on the disc electrode and then oxidized on the ring electrode. The results indicate that at a rotation rate of 20 Hz, when the disc electrode potential was in the region of 0.43 to 0.62 V and the ring electrode potential was at 1 V vs a standard calomel electrode (SCE), approximately 50% of the reacted pyrite was oxidized to ferric and sulfate ions and the other 50% was oxidized to sulfur and ferrous ions on the disc electrode. The latter was further oxidized to ferric ions on the ring electrode. As the disc electrode potential increased to 1.22 V vs SCE, more than 90% of the reacted pyrite was oxidized to ferric and sulfate ions on the disc electrode and less than 10% formed ferrous ions, which were further oxidized to ferric ions on the ring electrode. Copyright 1999 Academic Press.

Anesthesia for patients with carcinoid syndrome

Carcinoid syndrome, although rare, can create serious problems to the anesthetist, both by the nature and variability of clinical manifestations and by the complications that can occur peroperatively. Recent research has led to a better understanding of the pathophysiology of the disease process. However, modern medicine is far from unraveling the precise nature and physiological effects of all the peptide mediators produced by these tumors. The severity of symptoms does not predict the severity of perioperative complications, so that patients with minor preoperative symptoms may have significant intraoperative complications. While urinary 5-HIAA levels provide a good indicator of disease progression, they cannot predict the degree or type of physiological response to intraoperative tumor manipulation. Indeed, urinary 5-HIAA may be normal both in the presence of a clinical diagnosis of carcinoid syndrome and in the face of a peroperative carcinoid crisis. The keys to successful anesthetic management of patients with carcinoid syndrome are good communication between endocrinologist, anesthetist, and surgeon and preoperative optimization of the patient. This includes appropriate investigation and treatment of the effects of carcinoid peptides and the prevention of their release from tumors. If possible, advice should be sought from centers with experience at managing this group of patients. Octreotide has largely replaced the use of other drugs both for symptomatic control and acute treatment of the symptoms associated with carcinoid syndrome. However, other drugs, such as aprotinin, still have a significant place in the symptomatic control and treatment of peroperative complications, as serotonin is only one of a large variety of peptides responsible for the clinical effects of this disease. Anesthetic technique should be aimed at minimizing carcinoid mediator release, in response to stress it induction of anesthesia and tracheal intubation and during tumor manipulation. It is equally important to prepare for carcinoid crisis by, for example, ordering drugs, which are otherwise uncommonly used in the theater setting, ahead of time. Cardiovascular instability, particularly hypotension, is common, so that full monitoring and vigilance is vital to predict its onset. The current surgical view of management is that, while curative resection of carcinoid tumors less than 2 cm in diameter with no evidence of invasion or metastatic spread is appropriate, patients with disseminated disease should be medically managed unless symptom control is poor. The exceptions to this are those patients with early and correctable carcinoid cardiac disease and those who require palliative procedures such as defunctioning obstructed bowel. Survival rates in patients following excision of gastric and appendical carcinoid tumors approach those of the general population as a whole and the chance of metastasis is extremely low. Only two series have been published in the anesthetic literature on anesthesia for patients with carcinoid syndrome, although there are many single-case reports. Despite the rarity of this syndrome, further formal studies into the anesthetic management of this condition should be encouraged.

The involvement of dimethyl sulfoxide in a bacteriotoxic response of the Ames assay tester strains TA98 and TA100

Dimethyl sulfoxide is a widely accepted and recommended solvent in which to dissolve compounds to be tested for mutagenicity via the Ames Salmonella/mammalian microsome assay. Using tester strains TA98 and TA100, we observed a bacteriotoxic response with various fractions isolated from beer when dissolved in DMSO but not when dissolved in water. Further characterization of the role of solvent in simple model systems consisting of butanol, DMSO and bacteria strongly suggests a chemical reaction occurs between dimethyl sulfoxide and specific chemical constituents of the test substance, nutrient broth, or the Ames bacterial strains. The result of such an interaction could be misinterpreted as a toxic response to the test substance when, in fact, the bacteriotoxicity could be due to another compound, chemically distinct from the test substance.

The effect of fecapentaenes on nuclear aberrations in murine colonic epithelial cells

Fecapentaenes, human fecal mutagens of bacterial origin, were intrarectally administered to mice in suppository form. Despite the strong, positive mutagenic response of fecanpentaenes using Ames tester strains TA 98 and TA 100, no increase in nuclear aberrations, taken as a measure of genotoxicity in colonic epithelial cells, was observed over control levels. In fecapentaene treated animals, however, the incidence of mitotic figures was increased above control levels to values comparable to those observed in mice treated with the known colon carcinogen, N-ethyl-N-nitrosourea. Thus, it would appear that fecapentaenes are not cytotoxic to murine colonic epithelia as judged by the nuclear aberration assay.

The Kock pouch: initial experience and complications

The modified Kock continent internal reservoir procedure has been performed on 15 patients at our medical center since December 1984: 13 underwent simultaneous anterior exenteration for pelvic malignancy, 1 had conversion from an ileal conduit and 1 underwent cystectomy for refractory interstitial cystitis. There was no operative mortality. There were 3 early complications: a urinary leak from the pouch in 2 patients that required re-exploration to close the defect, and an enteric-Kock pouch fistula in 1 that required resection of the small bowel fistula and repair of the pouch defect. All 3 patients are doing well. The late complication in 3 cases was urinary incontinence of the efferent nipple valve with difficulty in catheterization of the stoma. Two patients have undergone revision with a new efferent nipple valve added on to the pouch and creation of a new stoma. One patient is completely dry and continent, 1 has tolerable intermittent leakage and refuses a further operation, and 1 is awaiting revision. Although the initial experience is small, we are encouraged by these results and believe that this procedure is an alternative form of urinary diversion for the properly selected patient.

Characterization of cytotoxic steroids in human faeces and their putative role in the etiology of human colonic cancer

It has been shown previously that chemically induced nuclear abeerrations in the murine colon are correlated with the carcinogenicity of the respective chemicals. Consequently, the nuclear aberration assay was utilized for the identification of putatife carcinogens in human faeces. Human fecal samples were fractionated by several chromatographic methods, and the assay led to the isolation of two substances. A combination of spectroscopic (mass, nuclear magnetic resonance, ultraviolet, and infrared) and chromatographic (HPLC and GLC) methods showed that they are 5-alpha- cholestan-3-one (I) and cholest-4-en-3-one (II). A number of C-27-C-30 steroids isolated from closely related fractions of feces were inactive in this assay. Thus I and II could play a role in etiology of large bowel cancer in humans.

Reconstitution of lipoproteins. I. Lipid-protein interaction of high density apoproteins, purified apoA-I and apoA-II with dimyristoyl-lecithin and dimyristoyl-lecithin:cholesterol vesicles studied by isomeric spin-labelled lecithins

Reconstitution of high density lipoprotein-like particles from lecithin, cholesterol, and high density lipoprotein apoproteins was studied. Sonicated mixtures of sn-3-dimyristoyl-lecithin and cholesterol (molar ratio 10:1) were incubated with total human plasma high density apoproteins and purified apoprotein A-I and apoprotein A-II in the presence of isomeric (5′-, 12′-, and 16′-(N-oxyl-4″,4″-dimethyloxazolidine)stearoyl) spin-labelled lecithin probes. The supernatant obtained after centrifugation of the incubation mixture at 12 000× g for 5 min contained reconstituted lipoproteins with an average protein:lipid weight ratio of 0.52–0.53. To determine the position of apoprotein A-I and apoprotein A-II with respect to the lipid bilayer, the thermotropic behaviour of reconstituted lipoproteins was monitored by electron spin resonance spectroscopy using isomeric spin-labelled lecithin probes. Comparison of experimental spectral parameters (transition temperature, temperature range, and cooperative unit) obtained from reconstituted lipoproteins with liposomes of dimyristoyllecithin and dimyristoyllecithin:cholesterol (10:1) showed a relative increase of transition temperature and broadening of the transition range with 5- and 12-(N-oxyl-4′,4′-dimethyloxazolidine)stearic acid containing lecithin probes when reconstituted lipoproteins contained either apoprotein A-I or apoprotein A-II. With 16-(N-oxyl-4′,4′-dimethyloxazolidine)stearic acid containing lecithin probe, the transition temperatures and the temperature range relative to those values measured with 5′- and 12′-(N-oxyl-4″,4″-dimethyloxazolidine) lecithin probes were higher and narrower, respectively, with a tendency towards values obtained for liposomes not containing apoproteins. The cooperative unit in dimyristoyl-lecithin:apoprotein recombinants monitored with 5′- and 12′-(N-oxyl-4″,4″-dimethyloxazolidine) lecithin probes was smaller than or approximately equal to those measured with 16′-(N-oxyl-4″,4″-dimethyloxazolidine) lecithin probes when these systems contained either apoprotein A-I or apoprotein A-II. These and other results indicate that apoproteins A-I and A-II in lipoprotein recombinants of the composition used in our study, are partially embedded within the hydrocarbon portion of the lipid bilayer of reconstituted lipoproteins but do not span the entire lipid bilayer. Relevance of these results to the mechanism of lecithin:cholesterol acyltransferase activation is discussed.

Reconstitution of lipoproteins. II. Lipid-protein interaction between dimyristoyl-lecithin and dimyristoyl-lecithin:cholesterol vesicles and purified apolipoprotein C-I and C-III2 studied by isomeric spin-labelled lecithins

The reconstitution of purified apolipoprotein C-I and C-III2 with sn-3-dimyristoyl-lecithin and sn-3-dimyristoyl-lecithin:cholesterol (10:1) vesicles was studied by electron spin resonance spectroscopy using isomeric 5'-, 12'-, and 16'-(N-oxyl-4",4"-dimethyloxazolidine)stearoyl spin-labelled lecithin probes. Results obtained from the temperature-induced changes of lipoprotein recombinants showed the hydrophilic nature of the lipid-protein interactions. The temperature-induced phospholipid phase transition, as measured by 5'-(N-oxyl-4",4"-dimethyloxazolidine)stearoyl spin-labelled lecithin probe in recombinants containing apoprotein C-1 or apoprotein C-iii2, is very broad and has a small cooperative unit indicative of extensive lipid-protein interactions occurring at the head group region of the phospholipid bilayer. When 12"- and 16'-(N-oxyl-4",4"-dimethyloxazolidine)stearoyl spin-labelled lecithins are used as probes in the same system, similar sharper and more cooperative lipid phase changes are detected. These results indicate a surface location for both apoprotein C-I and apoprotein C-III2 with respect to the phospholipid bilayer in lipoprotein recombinants with and without cholesterol.

Synthesis of spin-labelled 2-(16'-(N-oxyl-4'',4''-dimethyloxazolidine)stearoyl)-phosphatidylcholine

Chemical synthesis of spin-labelled lecithin 2-(16'-(N-oxyl-4'',4''-dimethyloxazolidine)stearoyl)-phosphatidylcholine was achieved by reaction of equimolar amounts of purified egg yolk lyso-lecithin with commercially available 16-(N-oxyl-4',4'-dimethyloxazolidine)stearic acid activated with N,N-carbonyldiimidazole. After purification by silicic acid column chromatography, spin-labelled lecithin was obtained in 52.2% yield and had an ester: phosphorus:spin molar ratio of 2.0:1.1:1.0. When dimyristoyl-phosphatidylcholine and dimyristoyl-phosphatidylcholine:cholesterol (10:1) liposomes, containing 2-(16'-(N-oxyl-4'',4''-dimethyloxazolidine)stearoyl)-phosphatidylcholine as a probe were examined for thermotropic changes monitored by electron spin resonance spectroscopy, transition temperatures of 24.0 and 24.2 degrees C, respectively, were obtained in a very good agreement with previously reported values obtained with different probes and by different techniques, and with our own differential scanning calorimetry measurements. The potential usefulness of synthetic 2-(16'-(N-oxyl-4'',4''-dimethyloxazolidine)stearoyl)-phosphatidylcholine as a spin-label probe in studies of lipid-protein interactions in biological membranes was discussed.

Magnetic Transitions Observed in Sulfide Minerals at Elevated Pressures and Their Geophysical Significance

The magnetic behavior of iron in chalcopyrite (CuFeS(2)) and pyrrhotite (Fe(7)S(8)) in the pressure range from 1 atmosphere to 20 kilobars has been studied by Mössbauer spectroscopy. Both chalcopyrite and pyrrhotite exhibit transitions from magnetically ordered to disordered states over the range from 5 to 16 kilobars. Both transitions, particularly the loss of ferrimagnetism in pyrrhotite, have geophysical consequences.