PubMed Health⌕ Search

Biomedical subjects

M J Worsey

Publications and source records attributed to M J Worsey.

12 recordsLinked to original sources
PubMed1992

An evaluation of color duplex scanning in the primary diagnosis and management of carotid body tumors.

Carotid body tumors present a diagnostic challenge. Despite technologic diagnostic advances, misdiagnosis resulting in blind biopsy or exploration through a limited incision still occur. Color duplex scanning has recently been used to evaluate carotid body tumors in our institution. A characteristic feature of these tumors found with this modality is wide splaying of the carotid bifurcation by a hypervascular mass. Color duplex scanning is the noninvasive modality of choice for the primary diagnosis of carotid body tumors. Additionally, it may be of use in screening for familial carotid body tumors and sequential follow-up of nonoperatively managed tumors.

Adult↗
PubMed1992

Perforation of a vein valve leaflet: a mechanism for incomplete valve incision during in situ bypass.

The modified Mills retrograde valvulotome has been our preferred instrument for valve incision for in situ saphenous vein bypass. In one case during completion angioscopy the valvulotome was identified to have perforated a posterior valve leaflet and left the leaflet intact. This intact leaflet was identified and incised under direct vision. Valve leaflet perforation by the valvulotome tip is proposed as one possible mechanism for incomplete valve lysis.

Aged↗
PubMed1991

Limitations of electroencephalographic monitoring in the detection of cerebral ischemia accompanying carotid endarterectomy.

An analysis was undertaken of 458 consecutive carotid endarterectomies performed over 6 years with the patient under general anesthesia and with electroencephalographic monitoring. Seventy patients (15%) had electroencephalographic changes suggestive of ischemia with carotid clamping and had shunts placed. Ischemic encephalographic changes occurred in 26% of patients with an occluded contralateral carotid artery, 21% of patients with a prior stroke history, and 12% of patients with no stroke history and a patent contralateral carotid artery. Nineteen strokes (4.1%), nine transient deficits (2.0%), and one death (0.2%) occurred in the 458 endarterectomies in this experience. Ten of the 19 strokes and five of nine transient deficits were immediately apparent when patients awoke from anesthesia. Five of 10 patients with immediate strokes and all five patients with immediate transient deficits had no ischemic electroencephalographic changes during the procedure. Two other patients with immediate strokes initially had ischemic electroencephalographic changes after carotid clamping that reversed with increased blood pressure or shunting. Therefore 7 of 10 patients with immediate strokes and all 5 patients with immediate transient deficits had electroencephalographs unchanged from baseline at completion of the procedure, and thus deficits not manifest by operative electroencephalographic changes developed. Our data do not support the tenet that electroencephalographic monitoring will always predict neurologic deficits accompanying carotid endarterectomy.

Aged↗
PubMed1978

Regulation of the degradative pathway enzymes coded for by the TOL plasmid (pWWO) from Pseudomonas putida mt-2.

Pseudomonas putida mt-2 carries a plasmid (TOL, pWWO) which codes for a single set of enzymes responsible for the catabolism of toluene and m- and p-xylene to central metabolites by way of benzoate and m- and p-toluate, respectively, and subsequently by a meta cleavage pathway. Characterization of strains with mutations in structural genes of this pathway demonstrates that the inducers of the enzymes responsible for further degradation of m-toluate include m-xylene, m-methylbenzyl alcohol, and m-toluate, whereas the inducers of the enzymes responsible for oxidation of m-xylene to m-toluate include m-xylene and m-methylbenzyl alcohol but not m-toluate. A regulatory mutant is described in which m-xylene and m-methylbenzyl alcohol no longer induce any of the pathway enzymes, but m-toluate is still able to induce the enzymes responsible for its own degradation. Among revertants of this mutant are some strains in which all the enzymes are expressed constitutively and are not further induced by m-xylene. A model is proposed for the regulation of the pathway in which the enzymes are in two regulatory blocks, which are under the control of two regulator gene products. The model is essentially the same as proposed earlier for the regulation of the isofunctional pathway on the TOL20 plasmid from P. putida MT20.

Enzyme Induction↗
PubMed1977

Characterization of a spontaneously occurring mutant of the TOL20 plasmid in Pseudomonas putida MT20: possible regulatory implications.

Pseudomonas putida MT20 carries a plasmid (TOL20) that codes for the enzymes responsible for the catabolism of toluene, m- and p-xylene to benzoate, and m- and p-toluate, respectively, followed by meta cleavage of the aromatic ring. Growth on 5 mM benzoate selects very strongly for (i) strains that have been cured of the plasmid and (ii) strains with an intermediate growth pattern (the B3 phenotype) that retain the ability to grow on toluene, m-xylene, and benzoate but are unable to grow on m-toluate. Both types of strains were selected because they are no longer able to oxidize benzoate by the plasmid pathway but instead use an alternative route, the ortho or beta-ketoadipate pathway, which is chromosomally coded and supports faster growth. Evidence that one strain with the B3 phenotype, MT20-B3, has a regulatory mutation that prevents induction of the meta-pathway enzymes by benzoate and m-toluate, but which enables them to be induced by toluene and m-xylene, is presented. The plasmid in this strain, as in most of the others with the same phenotype, is nonconjugative. Analysis of MT20-B3, together with revertants of it and other noninducible mutants, has led to a model for the regulation of the plasmid-coded enzymes in MT20, in which it is proposed that the early enzymes for degradation of m-toluate and benzoate are positively controlled by two regulator molecules, one of which interacts with toluene and m-xylene as inducers and the other of which interacts with benzoate and m-toluate. It is argued that MT20-B3 and strains with a similar phenotype arose as a result of a deletion of the gene coding for the second regulator molecule.

Benzoates↗
PubMed1977

Molecular sizes and relationships of TOL plasmids in Pseudomonas.

Plasmid deoxyribonucleic acid was isolated from thirteen Pseudomonas strains judged on genetic criteria to carry plasmids coding for the degradation of toluene and m- and p-xylenes (TOL plasmids). Most strains carried a single species, but two strains carried two size classes, and cells of a third strain contained plasmids ranging in size from 25 X 10(6) to 202 X 10(6) daltons. Some plasmids could be transformed into a Pseudomonas putida strain to yield Tol+ progeny. Plasmids from 5 of the 13 strains were indistinguishable on the basis of size and gel pattern of fragments after endonuclease digestion.

DNA Restriction Enzymes↗
PubMed1976

Ubiquity of plasmids in coding for toluene and xylene metabolism in soil bacteria: evidence for the existence of new TOL plasmids.

Thirteen bacteria have been isolated from nine different soil samples by selective enrichment culture on m-toluate (m-methylbenzoate) minimal medium. Eight of these were classified as Pseudomonas putida, one as a fluorescent Pseudomonas sp., and four as nonfluorescent Pseudomonas sp. All 13 strains appeared to carry TOL plasmids superficially similar to that previously described in P. putida mt-2 in that: (i) all the wild-type strains could utilize toluene, m-xylene, and p-xylene as sole carbon and energy sources, (ii) these growth substrates were metabolized through the corresponding alcohols and aldehydes to benzoate, m-toluate, and p-toluate, respectively, and thence by the divergent meta (or alpha-ketoacid) pathway, and (iii) the isolates could simultaneously and spontaneously lose their ability to utilize the hydrocarbons, alcohols, aldehydes, and acids, particularly during growth on benzoate, giving rise to cured strains which could grow only on benzaldehyde and benzoate of the aromatic substrates by the alternative ortho (or beta-ketoadipate) pathway. Eight of the isolates were able to transfer their TOL plasmids into their own cured strains, but only five were able to transfer them in interstrain conjugation into the cured strains, but only five were able to transfer them in interstrain conjugation into the cured derivative of P. putida mt-2. However, P. putida mt-2 was able to transfer its TOL plasmid into 11 of the cured isolates, and eight of these were able to retransmit this foreign plasmid in intrastrain conjugation with their own cured derivatives. Three of the isolates, MT 14, MT 15, and MT 20, differed significantly from the others in that the wild-type strains dissimilated the p-methyl-substituted substrates poorly, and also, during growth on benzoate, in addition to the cured derivatives, they gave rise to derivatives with a phenotype intermediate between the cured and wild-type strains, the biochemical and genetic nature of which has not been elucidated.

Benzoates↗
PubMed1975

Induction of prophage lambda during the division cycle of Escherichia coli.

When synchronous populations of Escherichia coli B/r (lambda) were exposed to low doses of ultraviolet light, the yield of infective centres varied with cell age. The yield was highest if the lysogenic bacteria were irradiated at a time which coincides approximately with the termination of rounds of DNA replication and it was lowest when dividing cells were irradiated. No such variation was detected following either irradiation of excision-defective lysogenic cells or thermal induction of lambdacI857 prophage in irradiated bacteria. It is suggested that the variation reflects a relationship between prophage induction and inhibition of cell division. This hypothesis is supported by data showing that irradiation promoted induction and curtailed division in E. coli K12 dnaA mutants which were dividing in the absence of DNA replication.

Cell Division↗
PubMed1975

Metabolism of toluene and xylenes by Pseudomonas (putida (arvilla) mt-2: evidence for a new function of the TOL plasmid.

Pseudomonas putida (arvilla) mt-2 carries genes for the catabolism of toluene, m-xylene, and p-xylene on a transmissible plasmid, TOL. These compounds are degraded by oxidation of one of the methyl substituents via the corresponding alcohols and aldehydes to benzoate and m- and p-toluates, respectively, which are then further metabolised by the meta pathway, also coded for by the TOL plasmid. The specificities of the benzyl alcohol dehydrogenase and the benzaldehyde dehydrogenase for their three respective substrates are independent of the carbon source used for growth, suggesting that a single set of nonspecific enzymes is responsible for the dissimilation of the breakdown products of toluene and m- and p-xylene. Benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase are coincidently and possible coordinately induced by toluene and the xylenes, and by the corresponding alcohols and aldehydes. They are not induced in cells grown on m-toluate but catechol 2,3-oxygenase can be induced by m-xylene.

Alcohol Oxidoreductases↗
PubMedDate not supplied

A prospective comparison of ankle/brachial indices and color duplex imaging in surveillance of the in situ saphenous vein bypass.

We performed routine postoperative surveillance of 124 consecutive in situ saphenous vein bypasses, using both ankle-brachial indices and color flow duplex imaging. Using a combination of low and high velocity criteria, color flow duplex identified 97% (37/38) of bypass and native artery inflow stenoses subsequently demonstrated by angiography, including 20 of 21 severe stenoses. A reduction in ankle-brachial index by greater than 0.15 identified 43% (16/38) of all stenoses, and only 10 of 21 severe stenoses. Revisional operations were performed in 30 bypasses for abnormalities detected by surveillance, resulting in a 3-year cumulative secondary patency of 87%. Color flow duplex is a superior technique for in situ bypass surveillance when compared to alterations in ankle-brachial indices. The identification of a bypass or inflow stenosis by routine surveillance and its subsequent operative treatment result in satisfactory long-term patency.

Aged↗