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Biomedical subjects

P J Walker

Publications and source records attributed to P J Walker.

At least 19 recordsLinked to original sources
PubMed1996

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↗
PubMed1995

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↗
PubMed1995

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↗
PubMed1995

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↗
PubMed1994

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↗
PubMed1994

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↗
PubMed1994

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↗
PubMed1994

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↗
PubMed1994

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↗
PubMed1994

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↗
PubMed1993

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↗
PubMed1993

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↗
PubMed1993

Initial clinical experience with a new model of mass transfer for peritoneal dialysis.

A clinical pilot study compared predictions of a new model of peritoneal dialysis mass transfer to measured weekly KT/V urea (KTu/V) and weekly creatinine clearance (Ccr) in liters per 1.73 m2 in 50 patients from five centers (40 CAPD, 10 CCPD). The Robertson et al. model is unique in that it does not require a 24-hour collection of dialysate. Instead, model predictions are based on the results of a standard 4-hour peritoneal equilibration test (PET) and appropriate demographic data. Analysis revealed 12 collection errors, 8 affecting the PET and 4 affecting 24-hour dialysate volume. PET drainage volume was low in six cases, excessive in two; 24-hour volume was incomplete in three, excessive in one. Similar errors were not found in the remaining 38 patients. In the 38 patients with correctly performed PET and dialysate collections, agreement between predicted and measured values was excellent.

Adult↗
PubMed1993

The use of endovascular techniques for the treatment of complications of aortic dissection.

Intravascular ultrasonography, balloon angioplasty, stent placement, and endovascular septal fenestration have been used in the evaluation and treatment of vascular complications of acute and chronic aortic dissection in five patients. There were three men and two women with an average age of 52 years (range 39 to 64 years). There were three chronic type A dissections, one acute type B, and one subacute type B dissection. Intravascular ultrasonography was used in all five cases. The three patients with chronic type A dissections underwent unilateral renal artery angioplasty (RA PTA) and stent placement; one patient with an acute type B dissection and associated fibromuscular dysplasia underwent bilateral RA PTA without stent placement. These procedures were performed to ameliorate severe hypertension. The final patient, with a subacute type B dissection, underwent iliac artery stenting to correct severe lower extremity ischemia. During a second intervention, this patient, who also had bowel ischemia and nonresolving acute renal failure, underwent balloon dilatation of a preexisting septal fenestration to augment visceral blood supply and bilateral RA PTA and stent placement in an effort to improve renal function. This patient eventually died of gut ischemia. After RA PTA and stent placement, one patient had a major intrarenal hemorrhage that required coil embolization and transfusion. In the four survivors, RA PTA and stent placement resulted in immediate improvement in blood pressure control. This response has been sustained during follow-up intervals ranging from 8 to 18 months (average 10 months). Intravascular ultrasonography can clearly demonstrate the pathologic anatomy associated with aortic dissection (even when angiography is ambiguous) and is essential for guiding therapeutic endovascular interventions. Further exploration of the efficacy of these endovascular techniques is warranted in this high-risk group of patients with aortic dissection who have appropriate clinical indications.

Acute Disease↗
PubMed1993

Catecholamine-secreting paraganglioma of the pterygopalatine fossa: case report.

The third reported case of a pheochromocytoma-like syndrome attributable to a catecholamine-secreting paraganglioma arising within the pterygopalatine fossa is documented. The 25-year-old, female subject was found to have raised levels of urinary catecholamines. At another center, a large vascular tumor was identified at lateral rhinotomy. Biopsy confirmed the diagnosis of paraganglioma. Tumor removal by a Fisch type-C approach to the sphenoid, parasellar region, and pterygopalatine fossa was complete and recovery uneventful.

Adult↗
PubMed1993

Early experience with cryopreserved saphenous vein allografts as a conduit for complex limb-salvage procedures.

PURPOSE: The lack of a suitable alternative to autogenous vein is often the limiting factor for complex lower extremity vascular reconstruction, especially when previously placed grafts have failed. Cryopreserved saphenous vein allografts have been used as an alternative conduit. This report reviews our early experience with this conduit in a series of complex redo revascularization procedures for limb salvage when no suitable autogenous vein was available. METHODS: Thirty-five patients underwent 39 lower extremity bypass grafts on 36 limbs. These patients had undergone a combined total of 72 prior revascularization procedures on the symptomatic limb, an average of two procedures per patient. Only five bypasses were performed as a primary procedure. There were 18 men and 17 women with a mean age of 71 years. Sixteen of the patients had diabetes. Thirty-four bypasses were performed for rest pain or ulceration, four for disabling claudication, and one for replacement of an aneurysmal vein graft. There were 35 femorotibial, three below-knee femoropopliteal, and one femoropedal reconstruction. Twenty-five grafts were constructed with cryopreserved vein only, whereas 14 were composite grafts; 10 were constructed with polytetrafluoroethylene, one with Dacron, and three with spliced native saphenous vein. The mean follow-up was 9 months (range 1 to 25 months). RESULTS: There was one early death (< 30 days) and two late deaths. Two patients died with a patent graft. There have been 12 early graft closures and an additional 17 late failures, resulting in primary cumulative graft patency rates of 67%, 56%, 43%, 28%, and 14% at 1, 3, 6, 12, and 18 months, respectively. Surgically correctable causes, including technical error and anastomotic stenosis, could be identified in 13 of the 29 graft failures. Salvage of failed grafts resulted in secondary cumulative graft patency rates of 87%, 77%, 61%, 46%, and 37% at these same intervals. There was no significant difference in primary or secondary graft patency rates related to diabetes, ABO graft compatibility, graft composition or orientation, indication for surgery, state of the outflow tract, or site of distal anastomosis. Limb salvage was attained in 24 (67%) of the 36 limbs. Two amputations were necessary despite patent grafts. CONCLUSIONS: Because of the poor overall graft patency rates, cryopreserved saphenous vein allografts should be used only as a last resort when no alternative autogenous conduit is available. Unless patency rates superior to those achievable with currently available prosthetic or biologic conduits can be attained by adjunctive measures such as routine anticoagulation or immunosuppressive therapy, the use of cryopreserved saphenous vein allografts for lower extremity revascularization should be deferred until improved preparation techniques provide a more durable conduit.

Adult↗
PubMed1993

Three-dimensional spiral computed tomographic angiography: an alternative imaging modality for the abdominal aorta and its branches.

PURPOSE: We sought to apply a new technique of computed tomographic angiography (CTA) to the preoperative and postoperative assessment of the abdominal aorta and its branches. METHODS: After a peripheral intravenous contrast injection, the patient is continuously advanced through a spiral CT scanner, while maintaining a 30-second breath-hold. Thirty-five patients with abdominal aortic, renal, and visceral arterial disease have undergone CTA. RESULTS: Diagnostic three-dimensional images were obtained in patients with aortic aneurysms (n = 9), aortic dissections (n = 4), and mesenteric artery stenoses (n = 4). The technique has also been used to assess vessels after operative reconstruction or endovascular intervention in 18 patients. These preliminary studies have correlated well with conventional arteriographic findings. In aneurysmal disease both the lumen and mural thrombus and associated renal artery stenoses are visualized. The true and false channels of aortic dissections and the perfusion source of the visceral vessels are clearly shown; patency of visceral and renal reconstruction or stent placement are confirmed. CTA is relatively noninvasive and can be completed in less time than conventional angiography with less radiation exposure. CONCLUSIONS: This initial experience suggests that CTA may be a valuable alternative to conventional arteriography in the evaluation of the aorta and its branches.

Adult↗