Biomedical subjects
Publications and source records attributed to J F White.
Ampelomyces and Phoma species are frequently confused with each other. Isolates previously attributed to the genus Ampelomyces were shown to be Phoma isolates through studies of their morphology and life cycle and ribosomal DNA internal transcribed spacer region 1 sequence analysis. Phoma glomerata can colonize and suppress development of powdery mildew on oak and may have utility as a mycoparasitic agent.
Mandrel-grown, mesh-reinforced vascular prostheses require adequate tissue coverage of the mesh for effective clinical function, particularly in low blood flow situations. Development of the ovine collagen-based Omniflowtrade mark vascular prosthesis has shown that the extent of this tissue cover is dependent on the interactions of the mandrel and the mesh with the sheep host. In the present study, the effects of chemical changes to the mesh have been examined. These data indicate that certain treatments of the mesh, particularly collagen or heparin, lead to increased tissue coverage while the number of sheep cells present and the ultrastructure of the resulting vessel remain unchanged.
The Omniflowtrade mark Vascular Prosthesis (OVP) has been manufactured and extensively tested in animal and human trials. It has mechanical and biological qualities superior to synthetic and biological conduits, particularly in low flow conditions. For further development into the smaller diameter coronary prostheses, the inner luminal surface is of paramount importance. In a previous study this inner surface was modified to produce a more uniformly thicker nonundulating surface. In this study the mandrels of these modified OVPs were treated with either collagen or heparin; the OVPs were evaluated for patency, tissue integration and wound healing, and endothelialization using a dog model comparable to that used to evaluate the unmodified OVP. In all instances, each of the modified prostheses were fully patent and had no signs of any deleterious effects caused by these modifications; no thrombus or aneurysms were visible. The tissue response was rapid with excellent new host collagen deposition within the vessel wall and minimal inflammatory and foreign body giant cells. Endothelialization was noted at the earliest explant time point in central regions of the prostheses, albeit that the histological picture at this time point appeared to reflect a complex atypical intimal layer.
A collagen tissue polymer composite manufactured in sheep and prepared in two different forms (wet and dry) was compared to polypropylene mesh and to a control group for effectiveness in the repair of an abdominal wall defect in a rabbit model. The wet and dry patches were shown to differ significantly in their pore size. The wet material was shown to retain its natural porosity and promoted neovascularization, tissue integration, cellular infiltration, and neomatrix formation compared to the dry collagen-polymer patch. This material was superior to the polypropylene mesh implant, which was associated with significant adhesions. The appearance of type VI collagen was the earliest sign of new cell infiltration and neomatrix formation within the implant. New deposition of type VI collagen was apparent throughout the thickness of the implant within 4 weeks, followed by type III collagen accumulation. Decreased porosity of the collagen component in the dry patches resulted in a totally nonintegrated implant. This induced a foreign-body capsule with minimal cellular tissue infiltration and no deposition of collagen types VI and III within the implant.
An absorbable membrane made from purified, pepsin-soluble collagen was compared to Interceed, an absorbable cellulose-based product, and to a control group for effectiveness in inhibiting the formation of adhesions between peritoneal surface injuries in adult rats. An adhesion scoring system was used to evaluate and compare the performance of the test materials with the control group in regard to the extent, tenacity, and type of any adhesions evident at 28 days following surgery. The collagen group performed significantly better (p < 0.05) than either the Interceed or control groups, showing fewer, less extensive adhesions. The collagen membranes resulted in either no or weak adhesions between the body wall and caecum. Adhesions in the Interceed group were quite variable and characterized by a marked peritoneal reaction in the caecal and body walls adjacent to adhesions. Control samples were characterized by close, dense fibrotic adhesions between the caecum and body wall. Both of the test materials showed some deficiencies in respect to their physical and handling properties that could be further improved for this indication.
Ulcerated or irregular heterogeneous carotid plaque as seen by duplex ultrasound can cause hemispheric transient ischemic attacks (TIAs) and/or a cerebrovascular accident, even if only associated with nonsignificant carotid stenosis on arteriography. The purpose of this study was to review our experience in patients who underwent a carotid endarterectomy after medical treatment had failed, based on pathologic findings detected by carotid duplex ultrasound with minimal disease on arteriography. The medical records of 14 patients who underwent carotid endarterectomy for TIA symptoms related to ulcerated or irregular heterogeneous plaques were analyzed. All had had preoperative carotid duplex ultrasound, arteriography, and cardiac and neurologic workups to rule out other causes for their TIAs. Medical treatment had failed in all of them. There were 10 men and four women whose median age was 68 years. Carotid duplex ultrasound showed irregular heterogeneous carotid plaque in all patients associated with 20% to 50% stenosis in 12 and approximately 50% to 60% stenosis in two. All had normal to < 20% stenosis on arteriograms. The duplex ultrasound findings were all confirmed at operation. All had an uneventful postoperative course with relief of symptoms. Carotid duplex ultrasound is superior to carotid arteriography in detecting irregular or ulcerative heterogeneous plaque associated with nonsignificant stenosis. Carotid duplex ultrasound can be used to determine the desirability of carotid endarterectomy after failed medical treatment in patients with classical and persistent TIA symptoms despite normal or minimal disease on arteriograms. A successful endarterectomy appears to predict an asymptomatic postoperative course.
PURPOSE: The early outcomes of carotid endarterectomy (CEA) with primary closure (PC) versus vein patch closure (saphenous vein [SVP] and jugular vein [JVP]) and polytetrafluoroethylene patch closure (PTFE-PC) were compared. METHODS: Three hundred ninety-nine CEAs were randomized into the following groups: 135 PC, 134 PTFE-PC, and 130 vein patch closure (SVP alternating with JVP). Surviving patients underwent a carotid color duplex ultrasonographic scan 1 month after surgery. Demographic characteristics were similar in all groups. RESULTS: The incidence of perioperative cerebrovascular accidents (CVAs) was 4.4% for PC, 0.8% for PTFE-PC, and 0% for vein patch closure (PC vs vein patch, p = 0.0165; PC vs all patching [vein and PTFE], p = 0.007). The perioperative CVA and reversible ischemic neurologic deficit (RIND) combined rates for all patching were superior to PC (1.5% vs 5.2%; p = 0.04). These combined rates were also superior for vein patch closure when compared with PC (0.8% vs 5.2%; p = 0.037). The mean diameter of the internal carotid artery was similar in patients who had perioperative neurologic deficits and those who did not. After 1 month of follow-up, 11.9% of the PC arteries were narrowed 50% or more in contrast to 2.3% for PTFE-PC, 3.1% for SVP, and 10.3% for JVP.
Spontaneous axillary-subclavian vein thrombosis in young patients produces long-term disability. Patients with secondary axillary-subclavian vein thrombosis usually require prolonged venous catheterization for chemotherapy or pacemaking. This study aimed to compare the early and late results of lytic versus anticoagulant therapy in the treatment of axillary-subclavian vein thrombosis, both spontaneous and secondary to central venous cannulation. Nine patients underwent conventional treatment (heparin and warfarin) (group 1), and 10 had initial lytic therapy followed by heparin and warfarin (group 2). Three patients had cervical or first rib resection. Thirteen patients had spontaneous thrombosis and six were secondary to central venous catheterization. The mean follow-up was 36 months. Two of nine patients (22%) in group 1 and eight of 10 patients (80%) in group 2 had total venous recanalization and symptom resolution (P = 0.018). In the spontaneous axillary-subclavian vein thrombosis subset, one of six patients (17%) in group 1 and five of seven patients (71%) in group 2 had total venous recanalization and symptom resolution (P = 0.078). The average difference in cost per patient between groups 1 and 2 was $19,039. In conclusion, lytic therapy appears superior to anticoagulation in the treatment of axillary-subclavian vein thrombosis. However, such treatment is more expensive and its benefits should be carefully weighed against the cost in each case.
Vpr is a virion-associated protein of human immunodeficiency virus type 1 (HIV-1) whose function in acquired immune deficiency syndrome (AIDS) has been uncertain. We previously employed yeast as a model to examine the effects of Vpr on basic cellular functions; intracellular Vpr was shown to cause cell-growth arrest and structural defects, and these effects were caused by a region of Vpr containing the sequence HFRIGCRHSRIG. Here we show that peptides containing the H(S/F)RIG amino acid sequence motif cause death when added externally to a variety of yeast including Saccharomyces cerevisiae, Kluyveromyces lactis, Candida glabrata, Candida albicans and Schizosaccharomyces pombe. Such peptides rapidly entered the cell from the time of addition, resulting in cell death. Elevated levels of ions, particularly magnesium and calcium ions, abrogated the cytotoxic effect by preventing the Vpr peptides from entering the cells. Extracellular Vpr found in the serum, or breakdown products of extracellular Vpr, may have similar effects to the Vpr peptides described here and could explain the death of uninfected bystander cells during AIDS.
Influenza NS2 protein was expressed in Saccharomyces cerevisiae using a copper-inducible promoter. The protein produced had a molecular weight of 13 kDa, was reactive with anti-NS2 antiserum and was localised to the yeast cell nucleus. Two-hybrid analysis identified a direct protein-protein interaction between NS2 and the M2 protein of the virus, involving the C-terminal 163 residues of M1. A filter-binding assay localised the M1 binding region to the C-terminal 70 amino acids of NS2.
The search for the ideal vascular prosthesis for below the knee replacement or coronary surgery continues. Long-term explant analysis of a biosynthetic composite vessel, the Omniflow Vascular Prosthesis I, has previously shown sound structural durability. An important determinant in defining durability has been the evaluation of the degree of persistence of the original biological components and the augmentation by new tissue. The development of a panel of specific monoclonal antibodies to collagens, that allow detection of new host collagen among the original collagens of the prosthesis has been a key factor. In the present study, these antibodies have been used to investigate the degree and rate of new collagen tissue infiltration in an improved version of the Omniflow prosthesis. The data show that new collagen types III and VI can be detected as early as 3 months in the adventitial tissue, and that complete tissue augmentation throughout the entire vessel wall is apparent by 6 months after implant. The novel explant analyses serve as a good predictive indication to the in vivo performance of the device and would be useful in rapid monitoring of further modifications to this vessel or to other collagen-based prostheses.
Methods are described for isolating the cell nests, subepithelial clusters of germinative cells, from salamander intestinal mucosa and for growing the nests in culture into polarized monolayers of intestinal epithelial cells. Cells were viable in culture for up to 3 wk. The capacity of the monolayer cells to engage in membrane transport was evaluated using the patch-clamp technique in the whole cell mode. L-Valine (25 mM) induced an inward current in small intestinal cells of 25.8 +/- 5.7 pA and depolarized the cell membrane 14.5 +/- 1.6 mV. L-Alanine and L-phenylalanine were similarly effective, whereas D-valine was ineffective. The Km of the transporter for valine was 90 mM. Replacement of bath Na with tris(hydroxymethyl)aminomethane eliminated the inward current induced by valine. The basal (solute-independent) inward current was also reduced by Na+ replacement. Glucose did not induce a Na+ current. In contrast to the effect of valine on small intestinal cells, large intestinal cells were unresponsive to valine. It is concluded that the cultured small intestinal cells possess Na-amino acid but not Na-sugar cotransport. This profile of behavior is characteristic of undifferentiated small intestinal cells. Primary cultures of salamander small intestinal cells should be useful for studying enterocyte function and the developmental biology of the small intestinal mucosa.
Phagemid vectors have been developed which promise to supersede hybridoma technology for the selection and production of human antibodies. We have modified an existing phagemid vector to improve the stability of synthesized soluble antibody fragments. The vector allows the antibody fragment to be produced: i) as a soluble protein incorporating a stable carboxyl terminal octapeptide (FLAG) or, ii) on the surface of a bacteriophage fused to a minor coat protein (the gene III protein). The antibody gene encoding the well characterized monoclonal antibody NC10 (an antibody that recognizes the neuraminidase of the influenza strain N9) was inserted as a single chain Fv construct into the phagemid vectors pHFA and pHFA/SacII. Western blotting, ELISA and electron microscopy studies showed that recombinant clones could be manipulated to either synthesize soluble protein into the periplasm or present the protein on the surface of bacteriophage. Cosynthesis of GroEL and GroES chaperonins resulted in complete proteolysis of the scFvNC10-FLAG-gIIIp fusion product and did not improve total phage production. Coexpression of chaperonins should be used with caution for library construction due to the expected selection pressure for protease resistant gene III fusions.
The Omniflow Vascular Prosthesis (OVP) is a truly integrated bio-synthetic composite of polyester mesh and ovine connective tissue components. In animal and human studies, the prosthesis has demonstrated long-term patency rates comparable and often better than alternate surgical replacements, with minimal aneurysmal or thrombotic problems. Immunohistological and TEM analysis of explants of OVP I provide good evidence for the excellent in vivo performance and are reviewed below. In addition, new data from explants of the OVP II, a later version of the Omniflow, are also described. These explant analyses have been enhanced by use of a library of highly specific monoclonal antibodies which can discriminate between collagens from different species.
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The Omniflow Vascular Prosthesis is a collagen--polyester composite which has been used successfully for peripheral vascular replacement. In this study, we have examined the distribution of the various connective tissue components and the ultrastructural organisation of these in order to understand and allow improvement of its functional properties. Using immunohistology with specific monoclonal antibodies, types I and III collagens were found to be the major components throughout the prosthesis. Type VI collagen was also present but was mainly associated with cells, particularly around the polyester mesh and silicone interfaces. While elastin was absent, two elastic tissue microfibrillar proteins were present uniformly throughout the structure. Ultrastructurally, clear differences existed between the local environments of the inner surface, which had formed around the silicone mandrel, the polyester mesh within the prosthesis, and the outer collagenous tissue which formed the central wall. At the inner surface, the amount of collagen was less and the orientation of these fibres was not well defined. The collagen fibrils in the polyester region were smaller than those of the main wall, which were well ordered and orientated along the axis of the device.
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