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Biomedical subjects

P Knox

Publications and source records attributed to P Knox.

At least 19 recordsLinked to original sources
PubMed1998

Adenoviral delivery of B7-1 (CD80) increases the immunogenicity of human ovarian and cervical carcinoma cells.

The majority of tumour cells do not express immune costimulatory molecules and this may account for their inability to stimulate directly an antitumour T cell response. Here we report on the construction of a recombinant E1/E3-deleted adenovirus encoding the human B7-1 costimulatory molecule. We explored the use of this vector for gene transfer to a number of human ovarian and cervical tumour cell lines, and to primary ovarian tumour material. Rapid and efficient gene transfer and expression was obtained in the majority of cases using a multiplicity of infection of 30 plaque forming units per cell. B7-1 expression was detectable at the cell surface within 12 h and was still detectable 10 days after infection. The immunogenicity of gene-modified tumour cells was tested in an allogeneic mixed lymphocyte tumour cell culture. Tumour cells expressing B7-1 were found to induce significantly higher levels of T cell proliferation than tumour cells modified with a control adenovirus carrying the beta-galactosidase gene. B7-1-induced T cell proliferation could be blocked by the addition of anti-B7-1 antibodies at the initiation of cocultures. These results support the rationale for use of adenovirally delivered B7-1 for genetic immunotherapy of ovarian and cervical cancer.

Adenoviridae↗
PubMed1995

Rebreathing improves accuracy of ventilatory monitoring.

OBJECTIVE: Our objective was to determine if rebreathing would reduce the gradient between arterial and end-tidal CO2 tension during positive-pressure ventilation. METHODS DESIGN: Experimental investigation. SETTING: Anesthesiology laboratory. SUBJECTS: A total of 10 dogs of either sex. INTERVENTIONS: Anesthesia (sodium pentobarbital) and muscle relaxation (pancuronium) were induced and animals were tracheally intubated and ventilated with a standard anesthesia ventilator and breathing circuit with CO2 absorber and then with a Mapleson D circuit with a fresh gas flow rate (VF) equal to alveolar ventilation plus the sampling flow rate of two capnometers. Rebreathing was varied by adjusting the respiratory rate (RR) so that minute ventilation (VE) to VF ratio was 1:1, 2:1, 3:1, and 4:1. RESULTS: CO2 production (ATPD) was determined as the product of expired concentration of CO2 and VE (BTPS). Alveolar ventilation (VA) was calculated by dividing the product of CO2 production and barometric pressure corrected for ambient temperature and water vapor pressure at body temperature by PaCO2. Tidal volume, RR, airway gas temperature, concentration of CO2 in gas at the tracheal tube and inlet/outlet of the mechanical ventilator, body temperature, arterial gas tensions and pH, heart rate, arterial blood pressure, and cardiac output were measured. Minute ventilation, mean arterial blood pressure and end-expiratory CO2 tension (PECO2) (BTPS) were calculated. During positive-pressure ventilation, concentration of inspired CO2 was zero with standard circuitry, and significantly increased with Mapleson D when VE:VF ratio was 1:1 (0.56 +/- 0.19%), 2:1 (1.97 +/- 1.30%), 3:1 (2.56 +/- 1.05%), and 4:1 (3.01 +/- 1.45%) (p < 0.05). PECO2 was 34.8 +/- 3.2 mm Hg during ventilation with the standard circuit, and significantly increased during ventilation with Mapleson D when VE:VF ratio was increased from 1:1 (35.4 +/- 2.5 mm Hg) to 2:1 (40.2 +/- 3.6 mm Hg) and was not further increased at a VE:VF ratio of 3:1 (41.8 +/- 2.7 mm Hg) or 4:1 (41.3 +/- 2.4 mm Hg). The selected fresh gas flow rate was appropriate, because PaCO2 remained unchanged regardless of VE:VF ratio, indicating PaCO2 was dependent on VF, not on VE. The gradient between PaCO2 and PECO2 during ventilation with the standard circuit was 6.6 +/- 3.0 mm Hg; during ventilation with Mapleson D, it decreased significantly when VE:VF ratio was increased from 1:1 (6.5 +/- 3.6 mm Hg) to 2:1 (2.9 +/- 1.5 mm Hg), but was not significantly reduced further at 3:1 (1.7 +/- 1.1 mm Hg) or 4:1 (1.8 +/- 0.5 mm Hg) (p < 0.05). CONCLUSIONS: Rebreathing with a Mapleson D circuit and a VF equal to VA permitted normal CO2 elimination. Arterial PCO2 to PECO2 gradient decreased significantly during rebreathing, thus improving the reliability of capnography for estimating arterial PCO2. Consideration should be given to using the Mapleson D as a rebreathing circuit.

Anesthesia, Closed-Circuit↗
PubMed1988

Plasminogen activation and lysis of blood clots induced by cells in vitro.

When human diploid fibroblasts were seeded onto the surface of blood clots, lysis of the clot occurred as a result of the release of cellular plasminogen activator. A number of aspects of this lysis were studied. 1. There was no significant difference in rates of lysis of whole blood clots, platelet-rich plasma clots, and platelet-poor plasma clots brought about by the same number of fibroblasts. 2. Clot lysis was promoted by nondividing cells and by proliferating cells. 3. Using cycloheximide to block protein synthesis it was found that the plasminogen activator released by fibroblasts had an active half-life of less than an hour. 4. When clots were washed prior to the addition of cells then lysis occurred at an increased rate. This was probably due to the removal of alpha 2-antiplasmin from the clots, since when antisera to alpha 2-antiplasmin was added to clots, lysis also proceeded at an increased rate. 5. Medium conditioned by fibroblasts did not promote clot lysis even when antiplasmin was removed by washing or by addition of antisera. 6. Cells had to be in direct contact with the clot in order to bring about lysis; when cells were separated from clots by permeable membranes there was no lysis. 7. When cross-linking of fibrin was reduced by the inhibition of transglutaminase, the rate of clot lysis was increased.

Cell Membrane Permeability↗
PubMed1988

Synovial fluid--its mass, macromolecular content and pressure in major limb joints of the rabbit.

Synovial fluid from rabbit elbow, shoulder, hip and knee was analysed to establish the normal levels of parameters relevant to fluid exchange viz. fluid mass per joint, hydraulic pressure, temperature, colloid osmotic pressure (COP), protein, albumin and glycosaminoglycan (GAG) concentrations. Fluid mass was greatest in the least congruous joint, the shoulder (43 +/- 4 mg), cf. 6 +/- 2 mg in the highly congruous hip. In the knee (24 +/- 4 mg) the mean thickness of the fluid layer was calculated to be 30 microns. Fluid pressure was subatmospheric in all joints (mean -2.8 +/- 0.4 cmH2O, elbow, to -5.7 +/- 0.3 cmH2O, knee), as in many other interstitial spaces. Colloid osmotic pressure was substantial (mean 11.4 +/- 0.9 cmH2O, shoulder, to 13.1 +/- 1.0 cmH2O, elbow), being 40-46% of serum level. Comparison of synovial fluid results with COP versus concentration curves in vitro indicated that the fluid's COP was primarily generated by its protein content (22-30 g l-1, 64% albumin) rather than GAG (4.0-5.8 g l-1). The GAG was 95% hyaluronate and 5% sulphated GAG. Algebraic summation of the hydraulic and colloid osmotic pressures of synovial fluid and serum indicated a net filtration gradient from blood to joint cavity. When serum COP was reduced by intravenous saline infusion, synovial fluid mass increased, in accordance with the ultrafiltration hypothesis of synovial fluid formation. The fluid's colloid concentration declined as volume increased. The relation was not a simple dilution curve, but indicated that the newly formed synovial fluid contained greater than or equal to 8 g protein l-1 (14.5% serum concentration); and that hyaluronate was entering the synovial cavity at a rate of greater than or equal to 6.5 micrograms h-1 per joint.

Animals↗
PubMed1987

Role of plasminogen, plasmin, and plasminogen activators in the migration of fibroblasts into plasma clots.

Human diploid fibroblasts were seeded onto or into plasma clots and different aspects of cell adhesion and migration were measured. The roles of plasminogen activators and plasmin were studied by either the removal of plasminogen from plasma prior to clotting or by the addition of 10 mM epsilon-aminocaproic acid, which brings about an inhibition of plasmin in this system. When cells were seeded onto the surface of plasma clots, rates of attachment, spreading, and migration were unaffected by plasminogen depletion or plasmin inhibition. In contrast, when cells were seeded into plasma clots, then, although the rates of cells spreading were unaffected, cell migration was abolished by plasminogen depletion or by plasmin inhibition. When cells were seeded onto the surface of plasma clots and the rate of migration into the clots was measured, there was an absolute requirement for plasmin activity; while fibroblasts migrated rapidly into the fibrin lattice of control clots, in the case of plasminogen-depleted clots, cells failed to penetrate the lattice. Focussing through a plasma clot revealed that fibroblasts do not migrate through the fibrin lattice but instead, localized areas of fibrinolysis are generated and cells migrate over the surface of the area of lysis.

Aminocaproic Acid↗
PubMed1987

Cell spreading on serum is not identical to spreading on fibronectin.

Adhesion and spreading of cell lines on dishes coated with serum-derived proteins were studied after removal of cell-surface proteoglycans. A mixture of glycosaminoglycans lyases from heparin-induced Flavobacterium heparinum removed 80% of the [35S]sulphate-labelled glycosaminoglycans from the surface of attached cells within 30 min, but this had little effect on cell morphology. The rate of cell attachment to dishes coated with serum was unaffected by prior treatment of cells with this mixture of glycosaminoglycan lyases. While a heparan sulphate lyase preparation abolished cell spreading in response to fibronectin there was no effect of the enzyme on the spreading mediated by vitronectin. These results suggest that, although heparan sulphate is required for spreading on purified fibronectin, the spreading stimulated by serum under routine culture conditions requires neither cellular heparan sulphate nor serum-derived fibronectin.

Blood↗
PubMed1986

Separating doctors' homes and doctors' offices: San Francisco, 1881-1941.

The urban medical delivery system includes not only the technological and scientific skills and apparatus used by health care practitioners but also those economic and social arrangements made by doctors that affect their ability to provide medical care. Among the most important of these is the location of health care facilities, especially doctors' offices. This paper traces the changing locations of doctors' offices in San Francisco between 1881 and 1941. Most specifically, it focuses on the separation of office from residence and the location of offices in the city. Changes in location began to occur during the urban transformation that occurred late in the nineteenth century. At that time, changes in the division of labor, the role of the family, and transportation and communications technology interacted with changes in science, medical technology and professional organization to alter the nature and location of the settings used to provide medical care. The health care delivery system is thus interpreted as the product of the overall dynamics of urbanization rather than the outcome simply of scientific discovery, medical technology and the influence of key medical practitioners and professional organizations.

California↗
PubMed1986

Outcome of surgery for obstructive jaundice is not associated with reduced levels of plasma fibronectin.

Reduced levels of plasma fibronectin have been implicated in the septicaemia and/or endotoxaemia that can accompany trauma or burns. Patients undergoing surgery for the relief of obstructive jaundice are also at risk of developing endotoxaemia or septicaemia. In this study, levels of plasma fibronectin were measured by immunoassay and bioassay in 16 such patients. No patient had a significantly reduced level of plasma fibronectin. Even in the case of patients developing a fatal septicaemia and general system failure there was no significant decrease in circulating fibronectin. It is concluded that measurement of plasma fibronectin is of no prognostic value and similarly infusion of fibronectin-rich cryoprecipitate would be of no therapeutic benefit.

Adult↗
PubMed1986

Role of fibronectin in the migration of fibroblasts into plasma clots.

The adhesion and migration of human diploid fibroblasts on plasma clots were measured. The role of plasma fibronectin was examined by depleting plasma of fibronectin before clotting. Fibronectin was not essential for cell adhesion and spreading, although rates were slightly slower on depleted clots. Rates of migration on the surface of clots were unaffected by fibronectin depletion. In contrast, fibronectin was an absolute requirement for migration of cells into plasma clots. Cells migrated rapidly into control clots but completely failed to penetrate the surface of fibronectin-depleted clots. The effect of depletion could only be reversed by adding fibronectin to depleted plasma before clotting. Adsorption of fibronectin after clotting failed to reverse the effect of depletion, suggesting that fibronectin had to be cross-linked by transglutaminase during the clotting process.

Absorption↗
PubMed1985

Chemiluminescence in neutrophils and Lettré cells induced by myxoviruses.

Luminol-mediated chemiluminescence in neutrophils is stimulated by Sendai virus and by influenza virus; Lettré cells also exhibit chemiluminescence (less than 10% of that of neutrophils), which is stimulated by Sendai virus and by influenza virus. Virally induced permeability changes are not responsible for chemiluminescence, since (i) extracellular Ca2+ inhibits permeability changes but stimulates chemiluminescence, and (ii) influenza virus, which induces permeability changes at pH 5.3 but not at pH 7.4, induces chemiluminescence at either pH. Other agents [zymosan, N-formyl-L-methionyl-L-leucyl-L-phenylalanine, 4-phorbol 12-myristate 13-acetate (phorbol ester), A23187] likewise induce chemiluminescence in the absence of permeability changes.

Animals↗
PubMed1984

Kinetics of cell spreading in the presence of different concentrations of serum or fibronectin-depleted serum.

A morphometric assay has been used to show that speed of cell spreading is sensitive to the level of serum in the surrounding growth medium. There was an inverse relationship between serum concentration and speed of spreading; as serum concentration was increased from 0.1% to 100% cells took progressively longer to become fully spread. The time taken to achieve complete spreading in serum concentrations of 0.1, 1.0, 10 and 100% serum was 45, 60, 105 and 240 min, respectively. At serum concentrations of 3% and above, fibronectin depletion had no effect on rates of spreading. Only at concentrations below 3% was there an effect of fibronectin depletion and although cells became fully spread in the depleted serum they took longer to do so in comparison to native serum. It is suggested that plasma fibronectin plays no role in serum-stimulated spreading at serum concentrations of 3% and above since at these concentrations rates of spreading are identical whether fibronectin is present or not. At concentrations of 3% and above spreading is mediated by the 70K spreading factor. At serum concentrations below 3% both fibronectin and 70K factor are effective. The reason for the lack of effect of fibronectin at higher serum concentrations is an inhibition by albumin and other plasma proteins. In contrast, 70K factor is not affected by exogenous protein concentration. The effect of exogenous protein concentration on cell adhesion is discussed in terms of cell migration between compartments that have different extracellular protein concentrations.

Animals↗
PubMed1983

The effect of the canine popliteal node on the composition of lymph.

The composition of afferent lymph draining into the canine popliteal lymph node was compared with that of the efferent lymph leaving the node. Both the protein and cellular composition were studied. In twenty-five greyhounds the protein concentration of efferent lymph was greater than that of afferent lymph collected from the same limb. Although the absolute level of protein varied greatly between dogs, in a particular animal there was a constant ratio between the protein content of afferent and efferent lymph. The concentration of protein in efferent lymph was approximately double that of afferent lymph. Chromatographic analysis of lymph and the use of radio-iodinated canine albumin indicated that the reason for the increased level of protein in the efferent lymph is that the popliteal node concentrates the protein in afferent lymph. Afferent lymph contained less than 3 X 10(3) cells/ml; efferent lymph contained between 0.5 X 10(6) and 4.3 X 10(6) cells/ml, 98% of which were lymphocytes. In different dogs there was no correlation between efferent lymphocyte density and afferent or efferent protein concentration; however, when an afferent lymphatic was perfused with solutions of different protein concentration, the lymphocyte number in the efferent fluid became greater as protein concentration in the afferent perfusate was increased. The concentrating effect of the node is discussed in terms of its significance to both fluid balance and immunological surveillance.

Animals↗