PubMed HealthSearch

Biomedical subjects

P J Walker

Publications and source records attributed to P J Walker.

At least 19 recordsLinked to original sources

Comparison of fresh and post-mortem human arterial tissue: an analysis using FT-IR microspectroscopy and chemometrics.

Fourier transform infrared (FT-IR) microspectroscopy and chemometric methods have been applied to the study of fresh and simulated post-mortem human arterial tissue. The results have shown that although physical differences were observed using light microscopy, no spectroscopic distinction could be made between these groups. The presence of collagen throughout the artery wall results in characteristic absorptions which may mask any biochemical changes that could otherwise have been detected by the FT-IR technique. Because the structure of the artery is unique, these findings should be regarded as tissue specific.

Collagen

Genome organization and transcription strategy in the complex GNS-L intergenic region of bovine ephemeral fever rhabdovirus.

A 1622 nucleotide region of the bovine ephemeral fever virus (BEFV) genome, located between the second glycoprotein (GNS) gene and the polymerase (L) gene, has been cloned and sequenced in Australian (BB7721) and Chinese (Beijing-1) isolates of the virus. In the Australian isolate, the region contains five long open reading frames (ORFs) organized into three coding regions (alpha, beta and gamma), each of which are bound by a consensus transcription initiation and transcription termination-polyadenylation-like sequences. The alpha coding region contains three long ORFs (alpha 1, alpha 2 and alpha 3). The alpha 1 ORF encodes a 10.6 kDa polypeptide which contains hydrophobic and highly basic regions characteristic of a viroporin. The alpha 2 ORF encodes a 13.7 kDa polypeptide and overlaps the alpha 3 ORF which encodes a 5.7 kDa polypeptide. The beta coding region contains a single long ORF encoding a polypeptide of 12.2 kDa. The gamma coding region, which does not occur in Adelaide River virus (ARV), contains a single long ORF encoding a polypeptide of 13.4 kDa. The Chinese isolate shares 91% nucleotide sequence identity with the Australian isolate. The organization of the alpha, beta and gamma coding regions is preserved and the sequences of the encoded polypeptides are similar to those of BB7721. The major transcription products of the region were identified in BB7721 as polycistronic alpha (alpha 1-alpha 2-alpha 3) and beta-gamma mRNAs. Sequence similarities in the BEFV alpha-beta and beta-gamma gene junctions, and the gamma-L and beta-L gene junctions of BEFV and ARV, suggest that the gamma gene may have evolved from the beta-gene by sequence duplication.

Amino Acid Sequence

Clinical experience with a bifurcated endovascular graft for abdominal aortic aneurysm repair.

PURPOSE: The purpose of this study was to test a transfemoral system of bifurcated endovascular graft insertion for aortic aneurysm repair. METHODS: Bifurcated endovascular grafts were inserted through bilateral femoral artery cutdowns in 41 patients. The results were assessed by completion angiography and follow-up computed tomography. RESULTS: The second half of the study included more aneurysms 6 cm or larger (p < 0.05) and more instances of short proximal neck (p < 0.05), proximal neck angulation (p < 0.05), and iliac angulation (p < 0.05). Despite the increasingly challenging anatomy, the results were better in the second half of the study as illustrated by the lower overall combined morbidity/mortality rate (15% vs 50%) and higher overall success rate (85% versus 65%). The mortality rate for the series as a whole was 7.5%. Mean follow-up was 18.8 months for the first 20 patients and 10.9 months for the second 20. The commonest complication in the first half of the study was graft thrombosis (n = 5). This complication was absent from the second half of the study because of routine adjunctive stenting. Two patients died of complications of endovascular repair. In both cases aneurysm rupture on the third postoperative day was associated with coagulopathy and angiographic signs of perigraft leak. CONCLUSION: Aneurysm exclusion with a bifurcated endovascular graft was feasible in a wide range of patients, but when the aneurysm was not entirely excluded from the circulation, the risk of rupture persisted.

Aorta, Abdominal

Vaccinia virus-expressed bovine ephemeral fever virus G but not G(NS) glycoprotein induces neutralizing antibodies and protects against experimental infection.

Two related glycoproteins (G and G(NS)) encoded in the bovine ephemeral fever virus (BEFV) genome were expressed from recombinant vaccinia viruses (rVV). Both proteins were detected in lysates of rVV-infected cells by labelling with D-[6-3H]glucosamine or by immuno-blotting. The recombinant G protein (mol. mass 79 kDa) appeared slightly smaller than the native G protein but reacted with monoclonal antibodies directed against all defined neutralizing antigenic sites (G1, G2, G3a, G3b and G4). The recombinant G(NS) protein (mol. mass 90kDa) was identical in size to the native G(NS) protein and failed to react by immuno-fluorescence with anti-G protein monoclonal or poly-clonal antibodies. Antisera raised in rabbits against rVV-G or rVV-G(NS) both reacted strongly by immuno-fluorescence and immuno-electron microscopy with BEFV-infected cells. The G protein was localized intracellularly in the endoplasmic reticulum/Golgi complex and at the cell surface associated with budding and mature virus particles. The G(NS) protein also localized intracellularly in the endoplasmic reticulum/Golgi complex; however, at the cell surface it was associated with amorphous structures and not with budding or mature virions. Rabbits vaccinated with rVV-G developed high levels of antibodies which neutralized BEFV grown in either mammalian or insect cells. Cattle vaccinated with rVV-G also produced neutralizing antibodies and were protected against experimental BEFV infection. In contrast, rVV-G(NS) vaccinated rabbits and cattle failed to produce neutralizing antibodies and, after challenge, BEFV was isolated from two-thirds of the vaccinated cattle.

Aedes

Transfemoral insertion of a bifurcated endovascular graft for aortic aneurysm repair: the first 22 patients.

The purpose of this study was to evaluate and optimize a system of transfemoral bifurcated graft insertion for endovascular repair of infrarenal aortic aneurysm. Grafts were inserted through bilateral femoral arteriotomies in 22 patients. Placement was guided by fluoroscopy. Results were assessed by completion angiography, with computed tomography scanning or duplex ultrasonography at 1, 3 and 6 months. The first 11 insertions were complicated by failed insertion in two cases, proximal leakage in one, graft limb thrombosis in five and wound infection in one. The second 11 insertions were complicated by retrograde leakage around the distal graft orifice in two patients. One of these was associated with aneurysm rupture, leading to the sole mortality of the series. There were no instances of graft migration or embolism. In conclusion, the lessons learned during the first 11 insertions were responsible for the improved results apparent in the second 11 insertions. When applied in properly selected patients, transfemoral insertion of a bifurcated graft is a reliable method of isolating an aortic aneurysm from the circulation.

Aortic Aneurysm, Abdominal

Adelaide River virus nucleoprotein gene: analysis of phylogenetic relationships of ephemeroviruses and other rhabdoviruses.

The nucleotide sequence of the Adelaide River virus (ARV) genome was determined from the 3' terminus to the end of the nucleoprotein (N) gene. The 3' leader sequence comprises 50 nucleotides and shares a common terminal trinucleotide (3' UGC-), a conserved U-rich domain and a variable AU-rich domain with other animal rhabdoviruses. The N gene comprises 1355 nucleotides from the transcription start sequence (AACAGG) to the poly(A) sequence [CATG(A)7] and encodes a polypeptide of 429 amino acids. The N protein has a calculated molecular mass of 49429 Da and a pI of 5.4 and, like the bovine ephemeral fever virus (BEFV) N protein, features a highly acidic C-terminal domain. Analysis of amino acid sequence relationships between all available rhabdovirus N proteins indicated that ARV and BEFV are closely related viruses (48.3% similarity) which share higher sequence similarity to vesiculoviruses than to lyssaviruses. Phylogenetic trees based on a multiple sequence alignment of all available rhabdovirus N protein sequences demonstrated clustering of viruses according to genome organization, host range and established taxonomic relationships.

Amino Acid Sequence

Agnathia (severe micrognathia), aglossia and choanal atresia in an infant.

A neonate is reported here, who was born with severe mandibular hypoplasia, complete absence of the tongue, unilateral choanal atresia, contralateral choanal stenosis and developed severe airway obstruction at birth. Arrested development of the ventral first branchial arch most likely underlies the clinical deficits. Most reported cases of agnathia have been lethal but the infant reported here has survived into infancy with a tracheostomy and feeding gastrostomy. Her clinical features, assessment and management are discussed.

Abnormalities, Multiple

Popliteal vein aneurysm: an unusual source of pulmonary embolus.

A 78 year old woman developed repeated major pulmonary emboli following nasal resection for recurrent basal cell carcinoma. Lower extremity venography performed prior to planned insertion of an inferior vena caval filter unexpectedly revealed a large thrombus-containing aneurysm of the proximal popliteal vein. The aneurysm was excised and the vein repaired by lateral suture. Anticoagulation was continued for 3 months postoperatively. There were no further episodes of pulmonary embolism and popliteal vein patency was confirmed by duplex ultrasound 3 months postoperatively. The literature pertaining to these rare popliteal venous aneurysms is reviewed.

Aged

Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms.

BACKGROUND: The usual treatment for thoracic aortic aneurysms is surgical replacement with a prosthetic graft, but the associated morbidity and mortality are considerable. We studied the use of transluminally placed endovascular stent-graft devices as an alternative to surgical repair. METHODS: We evaluated the feasibility, safety, and effectiveness of transluminally placed stent-graft to treat descending thoracic aortic aneurysms in 13 patients over a 24-month period. Atherosclerotic, anastomotic, and post-traumatic true or false aneurysms and aortic dissections were treated. The mean diameter of the aneurysms was 6.1 cm (range, 5 to 8). The endovascular stent-grafts were custom-designed for each patient and were constructed of self-expanding stainless-steel stents covered with woven Dacron grafts. RESULTS: Endovascular placement of the stent-graft prosthesis was successful in all patients. There was complete thrombosis of the thoracic aortic aneurysm surrounding the stent-graft in 12 patients, and partial thrombosis in 1. Two patients initially had small, residual patent proximal tracts into the aneurysm sac, but both tracts thrombosed within two months after the procedure. In four patients, two prostheses were required to bridge the aneurysm adequately. There have been no deaths or instances of paraplegia, stroke, distal embolization, or infection during an average follow-up of 11.6 months. One patient with an extensive chronic aortic dissection required open surgical graft replacement four months later because of progressive dilatation of the arch. CONCLUSIONS: These preliminary results demonstrate that endovascular stent-graft repair is safe in highly selected patients with descending thoracic aortic aneurysms. This new method of treatment will, however, require careful long-term evaluation.

Adult

Complex genome organization in the GNS-L intergenic region of Adelaide River rhabdovirus.

A 2341-nucleotide region of the Adelaide River virus (ARV) genome, located immediately downstream of the second glycoprotein (GNS) gene, has been cloned and sequenced. The region contains four long open reading frames (ORFs), the last of which represents a 1088-nucleotide fragment at the start of the ARV L gene. Between the GNS and L genes are two coding regions, separated by a single nucleotide (C), and each bounded by recognized transcription initiation (AACAG) and termination/polyadenylation (CATG[A]7) sequences. The first coding region comprises 682 nucleotides and contains two long ORFs (alpha 1 and alpha 2) which are in the same reading frame but separated by two consecutive stop codons. The alpha 1 ORF encodes a 12,545-Da polypeptide which contains highly hydrophobic and highly basic domains. The alpha 2 ORF includes a potential initiation codon 18 nucleotides downstream of the tandem stop codons and encodes a polypeptide of 11,951 Da. In ARV-infected cells, the alpha region is transcribed primarily as a long 4.7-kb polycistronic mRNA containing the G, GNS, alpha 1, and alpha ORFs. Direct sequence analysis of the mRNA indicated that the tandem stop codons between the alpha 1 and alpha 2 ORFs are retained in the transcript. The second coding region contains a single long ORF (beta) comprising 493 nucleotides which encodes a polypeptide with a calculated pl of 6.614 and molecular weight of 17,102 Da. The putative beta protein is similar in size to a protein which has been reported as a minor component of virions. The beta gene is transcribed as a 0.65-kb monocistronic mRNA for which the putative transcription termination/polyadenylation signal overlaps the L gene by 22 nucleotides.

Amino Acid Sequence

Effective vaccination of cattle using the virion G protein of bovine ephemeral fever virus as an antigen.

In a series of experiments, the envelope glycoprotein (G protein) of bovine ephemeral fever virus (BEFV) induced immunity against challenge with virulent virus. Protection correlated with the level of specific serum antibodies to G protein measured by a blocking ELISA test and with the level of neutralizing antibody. The optimum vaccination regimen consisted of two injections given 21 days apart at a dose rate of 0.32 microgram per cow of purified G protein emulsified in the adjuvant Quil A. This schedule conferred immunity for the duration of the preliminary experiment (46 days). Immunity to severe disease, but not to infection, remained for at least 12 months after vaccination, although BEFV could not be reisolated from vaccinated cattle following challenge. Unvaccinated cattle used as controls exhibited typical signs of clinical ephemeral fever and BEFV was recovered from all control animals following challenge.

Animals

Structural and antigenic analysis of the nucleoprotein of bovine ephemeral fever rhabdovirus.

The nucleotide sequence of the bovine ephemeral fever virus (BEFV) genome has been determined from the 3' terminus to the end of the nucleoprotein (N) gene. The 3' leader sequence comprises 50 nucleotides and shares a common terminal three nucleotides (3'-UGC-) and a downstream U-rich domain with vesicular stomatitis virus (VSV) and rabies virus. The N gene comprises 1328 nucleotides from the transcription initiation consensus sequence (AACAGG) to the conserved transcription termination-poly(A) sequence [CATG(A)7] and encodes a polypeptide of 431 amino acids with an estimated M(r) of 49,159 and a pI of 5.4. The deduced amino acid sequence of the BEFV N protein is similar to those of other mammalian rhabdoviruses and is more closely related in sequence to vesiculoviruses (VSV Indiana and New Jersey, Piry, Chandipura) than to lyssaviruses (rabies and Mokola). An almost full-length clone, 1301 bp in length, of the BEFV N gene and clones derived from 5'-terminal (559 bp) and 3'-terminal (742 bp) fragments were expressed in Escherichia coli as glutathione-S-transferase fusion proteins. A panel of 12 BEFV N protein-specific monoclonal antibodies was shown to react in immunoblots with fusion proteins containing the almost full-length N protein and the C-terminal fragment, but not the N-terminal fragment. Two of these antibodies also reacted with baculovirus-expressed rabies virus N protein. Polyclonal mouse ascitic fluids derived from BEFV, rabies virus and several other related viruses were also shown to cross-react in immunoblots with purified preparations of rabies virus and BEFV N proteins.

Amino Acid Sequence

External carotid endarterectomy for amaurosis fugax in the presence of internal carotid artery occlusion.

Two patients with occlusion of the internal carotid artery who were experiencing repeated episodes of transient monocular blindness in the ipsilateral eye were successfully treated with external carotid endarterectomy. The mechanisms for the production of symptoms in the presence of an internal carotid occlusion are discussed, including the anatomical pathways for embolization through collaterals between the internal and external carotid arteries. The indications, technique and results of external carotid endarterectomy are reviewed.

Aged

External septorhinoplasty in children: patient selection and surgical technique.

The external or open septorhinoplasty is used in children as young as 6 years of age. The primary indication for this procedure is the presence of nasal septal pathology anterior to the anterior nasal spine causing significant nasal airway obstruction. Meticulous attention to technique, especially the construction of a "new" septum, is essential for a successful outcome.

Child

External septorhinoplasty in children: Outcome and effect on growth of septal excision and reimplantation.

Outcome and effect on nasal growth of external septorhinoplasty was evaluated in 32 children. All had septal disease anterior to the nasal spine. In all cases, the cartilaginous septum was totally excised, refashioned, and then reinserted. Sixteen children with follow-up for more than 2 years were identified. Nine children had preoperative and postoperative nasal airflow studies and demonstrated a reduction in total nasal airway resistance, from a mean untreated value of 6.1 cm of water per centimeter per second preoperatively to a mean of 2.5 cm of water per centimeter per second postoperatively. IN 10 of these 16 children, six postoperative anthropometric measures and one index were determined, and these measurements were within the range of age- and sex-specific normative data from the Craniofacial Measurements Laboratory at the Hospital for Sick Children, Toronto, Ontario.

Adolescent

Adelaide river rhabdovirus expresses consecutive glycoprotein genes as polycistronic mRNAs: new evidence of gene duplication as an evolutionary process.

A 3914 nucleotide region of the Adelaide River virus (ARV) genome, located immediately downstream of the M2 gene, has been cloned and sequenced. The region contains two long open reading frames (ORFs). The first encodes a protein comprising 660 amino acids which shares extensive sequence homology with the virion G protein of bovine ephemeral fever virus (BEFV) and less but significant homology with other rhabdovirus glycoproteins. The size and structural characteristics of the product indicate that it represents the 90-kDa ARV virion G protein. The second ORF encodes a polypeptide of 609 residues with nine potential glycosylation sites which is most closely related to the BEFV non-structural glycoprotein (GNS). In infected mammalian cells, the ARV G and GNS genes are transcribed primarily as a polycistronic mRNA which appears to extend from the consensus sequence (AACAG) at the start of the G gene to the next recognized polyadenylation signal (CATG[A]7) located 697 nucleotides downstream of the GNS protein termination codon. Less abundant mRNAs which appeared to initiate at consensus sequences immediately preceding and following the GNS ORF and terminate at the same polyadenylation signal were also detected. Polyadenylation-like sequences at the end of each ORF do not appear to be recognized as transcription stop signals. Multiple sequence alignments and phylogenetic analyses indicated that the ARV G and GNS glycoproteins, like those of BEFV, are structurally related and appear to have evolved at different rates from a common ancestral gene. A copy-choice mechanism, involving upstream relocation of the polymerase during replication, is proposed to account for the evolution of the tandem glycoprotein genes.

Amino Acid Sequence