Case report: treatment of a carotid artery pseudoaneurism with a polyester covered nitinol stent.
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Aneurysm↗
Biomedical subjects
A M Cook
Publications and source records attributed to A M Cook.
Dynamic gradient-echo and fat-suppressed spin-echo contrast-enhanced MRI of the breast.
PURPOSE: To evaluate heavily T2-weighted, dynamic contrast-enhanced and fat-suppressed magnetic resonance imaging (MRI) of the breast in comparison with conventional imaging and fine needle aspiration cytology (FNAC). PATIENTS AND METHODS: Fifty patients with surgically/pathologically proven breast disease were examined pre-operatively by MRI. The majority, 45 patients, had invasive carcinoma. T1-weighted spin-echo, T2-weighted fast spin-echo (with chemical-shift-selective fat-suppression in 20 cases), rapid dynamic contrast-enhanced gradient-echo and post-contrast fat-suppressed T1-weighted images were obtained. Signal intensity changes during dynamic scanning were assessed qualitatively and quantitatively. Comparison was made with the results of X-ray mammography, ultrasound and fine needle aspiration cytology. RESULTS: Unenhanced MRI was inadequate for determining the location, extent or nature of most lesions even when fat-suppressed T2-weighted images were obtained. Following contrast injection, there was significantly greater enhancement of invasive carcinomas than normal parenchyma. Invasive carcinomas of ductal and lobular subtypes did not differ significantly in their enhancement profiles. Prominent enhancement of the lesion periphery, which was a feature in 33 out of 50 cases (the majority of which were invasive carcinomas) was not due to central tumour necrosis. In four cases, invasive carcinomas which were clearly visible on early dynamic scans could not be identified on post-contrast fat-suppressed images. Lesions that were more numerous or extensive than had been recognised clinically or mammographically were revealed by MRI in 14 patients, though MRI was no more specific than conventional assessment. Invasion of the chest wall was accurately predicted by MRI in three cases. There was excellent correlation between tumour size shown by MRI and histopathology. FNAC was accurate in predicting the final histological diagnosis except in those cases where samples were unsatisfactory. CONCLUSIONS: Contrast-enhanced MRI appears useful in the assessment of suspected malignant breast masses, especially in younger women with predominantly glandular breast tissue. Specificity is no better than FNAC but tumour extent and multifocality are more accurately disclosed than by conventional imaging techniques. Contrast-enhanced chemical-shift-selective fat-suppressed images are sub-optimal in a small proportion of cases (particularly where lesions are located posteriorly) and some benign breast disease may appear misleadingly conspicuous on such images. Morphological features and quantification of lesion enhancement during dynamic scanning presently offer only limited prospects for discrimination between various pathologies. Heavily T2-weighted sequences appear of marginal value.
Adolescent↗
Stereospecificity of hydride removal from NADH by reductases of multicomponent nonheme iron oxygenase systems.
The stereospecificity of hydride removal from the 4 position of the pyridine ring of NADH by reductases from all three classes of multicomponent nonheme iron oxygenases was examined. The class I and II reductases, modules of which show significant sequence similarity with and which belong to the ferredoxin-NADP+ reductase family of flavin-dependent oxidoreductases, transferred the pro-R hydrogen. By contrast, the class II enzymes, which do not show significant sequence similarity to the class I and III enzymes but modules of which belong to the glutathione reductase family of flavoenzymes, transferred the pro-S hydrogen.
Dioxygenases↗
Oxygenation and spontaneous deamination of 2-aminobenzenesulphonic acid in Alcaligenes sp. strain O-1 with subsequent meta ring cleavage and spontaneous desulphonation to 2-hydroxymuconic acid.
2-Aminobenzenesulphonic acid (2AS) is degraded by Alcaligenes sp. strain O-1 via a previously detected but unidentified intermediate. A mutant of strain O-1 was found to excrete this intermediate, which was isolated and identified by m.s., 1H- and 13C-n.m.r. as 3-sulphocatechol (3SC). Proteins from cell extracts of strain O-1 were separated by anion-exchange chromatography. A multicomponent oxygenase was observed to convert 1 mol each of NADH, O2 and 2AS into 1 mol each of 3SC, NH3 and NAD+. The enzyme presumably catalysed formation of the ring of a 2-amino-2,3-diol moiety, and elimination in the amino group led to a rearomatization. 3SC was further degraded via meta ring cleavage, which could be prevented by inactivation of the 3-sulphocatechol-2,3-dioxygenase (3SC23O) with 3-chlorocatechol. In Tris buffer, the separated 3SC23O catalysed the reaction of 1 mol each of 3SC and O2 involving a transient yellow intermediate, and release of 1 mol of sulphite and two organic products. The major product was identified by n.m.r. and by g.c./m.s. as 5-carboxypenta-2,4-dien-5-olide (CPDO), an indicator of formation of 2-hydroxymuconic acid (2HM). The second product was identified as the Z,E isomer of 2HM by comparison with authentic material. When the CPDO in the product mixture was chemically hydrolysed to (Z,E)-2HM, 1 mol of (Z,E)-2HM/mol of 3SC was observed. If oxygenation of 3SC by 3SC23O was carried out in phosphate buffer, only a single product was detected, a keto form of 2HM. This dioate was also formed from authentic (Z,E)-2HM in phosphate buffer. Formation of the natural product (Z,E)-2HM from the xenobiotic, 3SC, seems to involve oxygenation to the unstable 2-hydroxy-6-sulphonomuconic acid semialdehyde, which hydrolyses spontaneously to 2HM. There would appear to be at least one spontaneous reaction per enzyme reaction in this pathway.
Alcaligenes↗
3-Sulphocatechol 2,3-dioxygenase and other dioxygenases (EC 1.13.11.2 and EC 1.14.12.-) in the degradative pathways of 2-aminobenzenesulphonic, benzenesulphonic and 4-toluenesulphonic acids in Alcaligenes sp. strain O-1.
Alcaligenes sp. strain O-1 utilizes three sulphonated aromatic compounds as sole sources of carbon and energy for growth in minimal salts medium-benzenesulphonate (BS), 4-toluenesulphonate (TS) and 2-aminobenzenesulphonate (2AS). The degradative pathway(s) in 2AS-grown cells are initiated with membrane transport, NADH-dependent dioxygenation and meta ring cleavage. The specific activity of the NADH-dependent dioxygenation(s) varied with the growth phase and was maximal near the end of exponential growth for each growth substrate. Cells were harvested at this point from BS-, TS- and 2AS-salts medium. Cells grown with each sulphonated substrate could oxygenate all three compounds, but only 2AS-grown cells consumed 2 mol O2 per mol 2AS or BS or TS. BS- and TS-grown cells consumed 2 mol O2 per mol BS or TS but failed to oxygenate the product of oxygenation of 2AS, 3-sulphocatechol (3SC). These observations were repeated with cell extracts and we concluded that there were two sets of desulphonative pathways in the organism, one for 2AS and one for BS and TS. We confirmed this hypothesis by separating the degradative enzymes from 2AS-, BS- or TS-grown cells. A 2AS dioxygenase system and a 3SC-2,3-dioxygenase (3SC23O) were detected in 2AS-grown cells only. In both BS- and TS-grown cells a dioxygenase system for BS and TS was observed as well as a principal catechol 2,3-dioxygenase (C23O-III), neither of which was present in 2AS-grown cells. The 3SC23O was purified to near homogeneity, found to be monomeric (M(r) 42,000), and to catalyse 2,3-dioxygenation to a product that decayed spontaneously to sulphite and 2-hydroxymuconate. The 2AS dioxygenase system could cause not only deamination of 2AS but also desulphonation of BS and TS. The BS dioxygenase could desulphonate BS and apparently either desulphonate or deaminate 2AS. Strain O-1 thus seems to contain two putative, independently regulated operons involving oxygenation and spontaneous desulphonation(s). One operon encodes at least the 2AS dioxygenase system and 3SC23O whereas the other encodes at least the BS/TS dioxygenase system and C23O-III.
Alcaligenes↗
Microbial metabolism of sulfur- and phosphorus-containing xenobiotics.
The enzymes involved in the microbial metabolism of many important phosphorus- or sulfur-containing xenobiotics, including organophosphate insecticides and precursors to organosulfate and organosulfonate detergents and dyestuffs have been characterized. In several instances their genes have been cloned and analysed. For phosphonate xenobiotics, the enzyme system responsible for the cleavage of the carbon-phosphorus bond has not yet been observed in vitro, though much is understood on a genetic level about phosphonate degradation. Phosphonate metabolism is regulated as part of the Pho regulon, under phosphate starvation control. For organophosphorothionate pesticides the situation is not so clear, and the mode of regulation appears to depend on whether the compounds are utilized to provide phosphorus, carbon or sulfur for cell growth. The same is true for organosulfonate metabolism, where different (and differently regulated) enzymatic pathways are involved in the utilization of sulfonates as carbon and as sulfur sources, respectively. Observations at the protein level in a number of bacteria suggest that a regulatory system is present which responds to sulfate limitation and controls the synthesis of proteins involved in providing sulfur to the cell and which may reveal analogies between the regulation of phosphorus and sulfur metabolism.
Bacteria↗
Desulfonation of linear alkylbenzenesulfonate surfactants and related compounds by bacteria.
Pseudomonas putida S-313 (= DSM 6884) grew in sulfate-free medium when the sole sulfur source supplied was one of several arylsulfonates involved in the synthesis, application, or biodegradation of linear alkyl-benzenesulfonate (LAS) surfactants. 2-(4-Sulfophenyl)butyric acid, 4-n-butyl-1-methyl-6-sulfotetralin, and 4-toluenesulfonic acid were each completely utilized during growth, as were the model LAS 1-(4-sulfophenyl) octane and the arylsulfonate dyestuff Orange II. The product in each case was the corresponding phenol, which was identified by gas chromatography-mass spectrometry or H nuclear magnetic resonance. Stoichiometric conversion of 4-toluenesulfonic acid to 4-cresol was observed. The molar growth yields observed were 2.4 to 2.8 kg of protein per mol of S, which were comparable to the yield for sulfate. Commercial LAS disappeared from growth medium inoculated with strain S-313, but negligible growth occurred; digestion of cells in alkali led to recovery of the LAS mixture, which seemingly sorbed to the cells. However, mixed culture L6 was readily obtained from batch enrichment cultures containing commercial LAS as a sole sulfur source and an inoculum from domestic sewage. Culture L6 desulfonated components of the LAS surfactant to the corresponding phenols, which were identified by gas chromatography-mass spectrometry. Compounds with shorter alkyl chains were desulfonated preferentially, as were the centrally substituted isomers. In the presence of 200 muM sulfate, culture L6 grew well and LAS disappeared, although this was due purely to sorption, as shown by digestion of the cells in alkali. Thus, under sulfate-limited conditions, LAS can be desulfonated directly.
Journal Article↗
Terephthalate 1,2-dioxygenase system from Comamonas testosteroni T-2: purification and some properties of the oxygenase component.
Comamonas testosteroni T-2, grown in terephthalate (TER)-salts medium, synthesizes inducible enzymes that convert TER to (1R,2S)-dihydroxy-3,5-cyclohexadiene-1,4-dicarboxylic acid (DCD) and protocatechuate (PC). Anion-exchange chromatography of cell extracts yielded two sets of fractions, R and Z, that were necessary for oxygenation of TER to DCD; we termed this activity the TER dioxygenase system (TERDOS). An NAD(+)-dependent DCD dehydrogenase, which converted DCD to PC, overlapped all fractions R. No significant purification from fraction R, which contained an NADH-dependent reductase function(s) of TERDOS, was attained. Fraction Z, at the end of the gradient, contained essentially one protein, which was further purified by hydrophobic interaction chromatography. This component, Z, had the UV-visible spectrum and electron paramagnetic resonance characteristics of a Rieske [2Fe-2S] protein and was considered to be the oxygenase. M(r)s of about 126,000 for oxygenase Z under native conditions were observed. Oxygenase Z consisted of two subunits, alpha and beta, with M(r)s of 49,000 and 18,000, respectively, under denaturing conditions. We presume that this oxygenase has an alpha 2 beta 2 structure. The sequences of the N-terminal amino acids of each subunit were determined. The activity of the purified enzyme was enhanced about fivefold by addition of Fe2+. In the presence of O2, NADH, and fraction R, component Z catalyzed the stoichiometric transformation of TER to PC, with the intermediate formation of DCD. The reaction was confirmed as a dioxygenation when we observed incorporation of two oxygen atoms from 18O2 into PC. The substrate range of TERDOS appeared to be narrow; apart from TER, only 2,5-dicarboxypyridine and 1,4-dicarboxynaphthalene (of 11 compounds tested) were converted to a product.
Biodegradation, Environmental↗
Reproducibility of bone ages when performed by radiology registrars: an audit of Tanner and Whitehouse II versus Greulich and Pyle methods.
This audit analysed the Tanner and Whitehouse II twenty bone (TW2) method of bone age assessment which was used in our department, and compared it with the Greulich and Pyle (GP) method. 50 previous bone ages were independently re-calculated by each of three registrars using both techniques, with the time taken to perform each assessment being recorded. For each method the interobserver variation was analysed in terms of the spread of results. The intraobserver variation in TW2 was determined by comparing the bone age originally reported with that subsequently calculated on the same film by the same registrar. The average spread of results was 0.74 years for TW2 method, and 0.96 years for the GP method and this difference is not statistically significant at the 5% level. The average intraobserver variation to TW2 was 0.33 years, but with 95% confidence limits of -0.87 to +1.53 years. The average time taken was 7.9 min for TW2 and 1.4 min for GP assessments. It was concluded that the GP method gave similar reproducibility and was faster than the TW2 method. Following clinical discussion the routine departmental bone age assessment method was changed from the TW2 to the GP method.
Age Determination by Skeleton↗
Dynamic contrast-enhanced and fat suppressed magnetic resonance imaging in suspected recurrent carcinoma of the breast: preliminary experience.
20 women with suspected recurrent breast cancer who had undergone previous breast-conserving operations were investigated using dynamic contrast-enhanced gradient echo (GRE) and fat suppressed spin echo (SE) magnetic resonance (MR) imaging. Histologically confirmed recurrent tumour was readily recognized on dynamic GRE scans by virtue of rapid, early and avid enhancement. Benign scars enhanced more slowly and reached lower magnitudes of enhancement. Fat suppressed SE images, which were typically acquired 10 min after contrast administration, were sensitive for the detection of tumour recurrence but lacked specificity. Early scanning after contrast administration offers the best prospects for distinguishing tumour recurrence from benign scarring. The criteria used to distinguish these two entities are highly dependent on the scan technique and the time at which images are obtained post-contrast.
Aged↗
Purification of two isofunctional hydrolases (EC 3.7.1.8) in the degradative pathway for dibenzofuran in Sphingomonas sp. strain RW1.
Sphingomonas sp. strain RW1, when grown in salicylate-salts medium, synthesized the enzymes for the degradation of dibenzofuran. The reaction subsequent to meta cleavage of the first benzene ring was found to be catalyzed by two isofunctional hydrolases, H1 and H2, which were purified by chromatography on anion exchange, hydrophobic interaction and gel filtration media. Each enzyme was able to hydrolyze 2-hydroxy-6-oxo-6-(2-hydroxyphenyl)hexa-2,4-dienoate and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate to produce salicylate and benzoate, respectively. SDS/PAGE of each purified enzyme showed a single band of M(r) 31,000 (H1) or 29,000 (H2). The N-terminal amino acid sequences of the two proteins showed 50% homology.
Bacteroidetes↗
The use of the Wallstent in aorto-iliac vascular disease.
Forty-three patients had self-expanding endovascular Wallstents inserted for aorto-iliac arterial disease. A total of 59 Wallstents were inserted into 50 iliac arteries. There were 27 males and 16 females with a mean age of 62.51 years. Included in the series were 19 iliac occlusions, 21 severe atheromatous disease of the aortoiliac segment, two severe dissections following conventional angioplasty and one re-stenosis of a previously dilated iliac segment. All of the stents were successfully deployed but there were five significant complications. One case of distal embolism was treated by surgical embolectomy but the other four were treated by an additional percutaneous technique. At follow-up after 6 months all patients remain symptomatically improved. Aorto-iliac stenting is a cost-effective treatment in selected cases of severe aorto-iliac disease.
Aortic Diseases↗
The use of the Wallstent endovascular prosthesis in the treatment of malignant obstruction of the superior vena cava.
Seventeen patients (10 men and seven women) aged 48-76 years (mean 63.4) who were suffering from malignant superior vena caval obstruction had Wallstents implanted percutaneously to relieve the obstruction. Fifteen of the patients had previously been treated by radiotherapy or chemotherapy, with either failure to remit or later recurrence. Six patients required thrombolysis prior to stenting. All patients had rapid relief of the obstructive symptoms. This was sustained in 15 patients to date or at death. Two patients, both of whom had pre-stent lysis, developed stent thrombosis following withdrawal of anticoagulation at 4 months and 7 days respectively. Stenting has been shown to be extremely effective at relieving superior vena caval obstruction in these patients and is usually the only method available in this condition when other treatments fail. Whether all patients presenting with malignant superior vena caval obstruction should be stented de novo remains to be proven.
Aged↗
Dichloromethane as the sole carbon source for an acetogenic mixed culture and isolation of a fermentative, dichloromethane-degrading bacterium.
Dichloromethane (DCM) is utilized by the strictly anaerobic, acetogenic mixed culture DM as a sole source of carbon and energy for growth. Growth with DCM was linear, and cell suspensions of the culture degraded DCM with a specific activity of 0.47 mkat/kg of protein. A mass balance of 2 mol of chloride and 0.42 mol of acetate per mol of DCM was observed. The dehalogenation reaction showed similar specific activities under both anaerobic and aerobic conditions. Radioactivity from [14C]DCM in cell suspensions was recovered largely as 14CO2 (58%), [14C]acetate (23%), and [14C]formate (11%), which subsequently disappeared. This suggested that formate is a major intermediate in the pathway from DCM to acetate. Efforts to isolate from culture DM a pure culture capable of anaerobic growth with DCM were unsuccessful, although overall acetogenesis and the partial reactions are thermodynamically favorable. We then isolated bacterial strains DMA, a strictly anaerobic, gram-positive, endospore-forming rod, and DMB, a strictly anaerobic, gram-negative, endospore-forming homoacetogen, from culture DM. Both strain DMB and Methanospirillum hungatei utilized formate as a source of carbon and energy. Coculture of strain DMA with either M. hungatei or strain DMB in solid medium with DCM as the sole added source of carbon and energy was observed. These data support a tentative scheme for the acetogenic fermentation of DCM involving interspecies formate transfer from strain DMA to the acetogenic bacterium DMB or to the methanogen M. hungatei.
Bacteria, Anaerobic↗
Dibenzofuran 4,4a-dioxygenase from Sphingomonas sp. strain RW1: angular dioxygenation by a three-component enzyme system.
Sphingomonas sp. strain RW1 synthesized a constitutive enzyme system that oxygenated dibenzofuran (DBF) to 2,2',3-trihydroxybiphenyl (THB). We purified this dibenzofuran 4,4a-dioxygenase system (DBFDOS) and found it to consist of four components which catalyzed three activities. Two isofunctional, monomeric flavoproteins (components A1 and A2; M(r) of about 44,000) transferred electrons from NADH to the second component (B; M(r) of about 12,000), a ferredoxin, which transported electrons to the heteromultimeric (alpha 2 beta 2) oxygenase component (C; M(r) of alpha, 45,000; M(r) of beta, 23,000). DBFDOS consumed 1 mol each of NADH, O2, and DBF, which was dioxygenated to about 1 mol of THB; no intermediate was observed. The reaction was thus the dioxygenation of DBF at the 4 and 4a positions to give a diene-diol-hemiacetal which rearomatized by spontaneous loss of a phenolate group to form THB. Components A1 and A2 each reduced dichlorophenolindophenol but had negligible activity with cytochrome c; each lost the yellow color, observed to be flavin adenine dinucleotide, upon purification. Component B, which transported electrons to the oxygenase or cytochrome c, had an N-terminal amino acid sequence with high homology to the putidaredoxin of cytochrome P-450cam. The oxygenase had the UV spectrum of a Rieske iron-sulfur center. We presume DBFDOS to be a class IIA dioxygenase system (EC 1.14.12.-), functionally similar to pyrazon dioxygenase.
Amino Acid Sequence↗
Uptake of 4-toluene sulfonate by Comamonas testosteroni T-2.
The mechanism of transport of the xenobiotic 4-toluene sulfonate (TS) in Comamonas testosteroni T-2 was investigated. Rapid uptake of TS was observed only in cells grown with TS or 4-methylbenzoate as a carbon and energy source. Initial uptake rates under aerobic conditions showed substrate saturation kinetics, with an apparent affinity constant (Kt) of 88 microM and a maximal velocity (Vmax) of 26.5 nmol/min/mg of protein. Uptake of TS was inhibited completely by uncouplers and only marginally by ATPase inhibitors and the phosphate analogs arsenate and vanadate. TS uptake was also studied under anaerobic conditions, which prevented intracellular TS metabolism. TS was accumulated under anaerobic conditions in TS-grown cells upon imposition of an artificial transmembrane pH gradient (delta pH, inside alkaline). Uptake of TS was inhibited by structurally related methylated and chlorinated benzenesulfonates and benzoates. The results provide evidence that the first step in the degradation of TS by C. testosteroni T-2 is uptake by an inducible secondary proton symport system.
Aerobiosis↗
Proteins induced by sulfate limitation in Escherichia coli, Pseudomonas putida, or Staphylococcus aureus.
Two-dimensional gel electrophoresis of proteins from Escherichia coli, Pseudomonas putida, and Staphylococcus aureus, grown with methionine or one of a variety of organosulfates and organosulfonates as the sole source of sulfur, showed expression of specific sets of 7 to 14 proteins which were not observed during growth with sulfate or cysteine for all three species or with thiocyanate for P. putida and S. aureus. Under the same conditions, arylsulfatase activity in P. putida and S. aureus was seen to increase by up to 140-fold, suggesting that the proteins induced under these conditions may be involved in sulfur metabolism. We propose that these proteins are members of a sulfate starvation-induced stimulon.
Arylsulfatases↗
A study of the application of Fitts' law to selected cerebral palsied adults.
Fitts' Law was applied to the evaluation of discrete aimed arm movements in one dimension performed by 6 adults with cerebral palsy and 6 adults with normal movement. Targets (1.27, 3.81, 6.35, 8.89 cm in width) placed at distances of 20.32, 30.48, 40.64, and 50.80 cm provided Indices of Difficulty of 2.19 to 6.32 bits. A video game was used for the signal to move. The t tests for corrected means showed that the cerebral palsied group had greater reaction and movement times than than the normal group. Linear regression analyses for pooled data and for the individual cerebral palsied subjects showed (a) no relationship between reaction time and Index of Difficulty for either group and (b) a negative, linear relationship between reaction time and Index of Difficulty for 1 cerebral palsied subject. Movement time was linearly and positively related to the Index of Difficulty for the normal group but not for the cerebral palsied group. Two cerebral palsied subjects had movement times which conformed to Fitts' Law. While the exceptions to Fitts' Law may be due to the limited range of movement and spasticity caused by severe cerebral palsy, there are indications that two of the cerebral palsied subjects were performing ballistic rather than visually guided aimed movements. Fitts' Law may still apply when the distances and target positions are individualized to conform to subjects' specific limitations and when the signal to move is auditory rather than visual.
Adult↗