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P Barfort

Publications and source records attributed to P Barfort.

13 recordsLinked to original sources
PubMed1990

Hypothermic preservation of rabbit kidneys for 48 hours using low ionic strength solutions.

Microwaves offer the prospect of rapid and uniform heating of frozen organs. This is significant in the context of cryopreservation, and particularly of vitrification, because microwave heating may help to avoid crystallization or recrystallization of ice during warming, minimize any effects of high cell density, and reduce thermal-mechanical stresses. Previous work has established a rationale for reducing the ionic strength of solutions used to prepare tissues for microwave heating, since this permits the use of lower frequencies, which makes heating more uniform, without increasing the risk of thermal runaway (T. P. Marsland, S. Evans, and D. E. Pegg, Cryobiology 24, 311-323, 1987). In this paper we report a study of two possible low ionic strength perfusates, in rabbit kidneys, using 48 hr of hypothermic storage and autotransplantation as the test system. This model was chosen because there is a great deal of basic information about it. Both a single-pass "flush" preservation solution and a solution designed for continuous perfusion gave excellent results. The continuous perfusion system, which would be the more suitable for introducing cryoprotectants, gave five of five surviving animals with peak serum creatinine levels of 353-555 mumol/liter normal histology in three cases, and only very minor damage in the other two. There would therefore seem to be no obstacle to the use of perfusates having a low ionic strength in renal cryopreservations studies.

Animals↗
PubMed1988

Introduction and removal of cryoprotective agents with rabbit kidneys: assessment by transplantation.

Rabbit kidneys were perfused with up to 4 M glycerol or propane-1,2-diol (propylene glycol, PG) in three vehicle solutions: one normokalemic and made hypertonic with mannitol (HP5), one hyperkalemic but without mannitol (HP6), and one hyperkalemic and with mannitol (HP7). Subsequent function was assessed by autotransplantation. Up to 3 M glycerol in HP5 was well tolerated but not in HP6 or HP7. Conversely, up to 3 M PG in HP7 was compatible with excellent post-transplant function, but the same concentration in HP5 was severely damaging. PG (4 M) in either solution was severely injurious and no kidneys survived perfusion with this concentration. Vascular resistance was well controlled by the vehicle solutions with mannitol, but it was generally higher during perfusion with the hyperkalemic HP7 compared with the normokalemic HP5. No kidneys perfused with 3 M solutions of either of the cryoprotective agents and cooled briefly to -6 degrees C without freezing had any post-transplant function, and neither did kidneys perfused with 3 M PG or 4 M glycerol tolerate slow cooling to -80 degrees C and warming. The need to optimize perfusate composition for the CPA being used is clear, and the dramatic increase in toxicity of PG when the concentration exceeds 3 M supports the suggestion that mixtures of PG and glycerol should be considered. The observation of damage at high subzero temperatures, before freezing has occurred, requires further detailed study.

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PubMed1987

Activation of fibrinolysis during xenoperfusion.

Ten rabbit kidneys were perfused at 80 mm Hg, 37 degrees C, with oxygenated recirculating heparinized human blood. These experiments were compared to another ten perfusion experiments where 1 unit/ml porcine plasmin was added to the human blood one hour before the perfusion, at which time the fibrinolytic activity was significant and the fibrinogen concentration under the detection limit. Rejection, determined as time until blood flow decreased to 2 ml/min, was not significantly delayed by addition of plasmin. At the end of the experiments, the fibrinolytic activity in the control experiment had increased above the activity in the plasmin added experiments, although the fibrinogen concentration was almost unchanged. Histological examinations demonstrated a decreased platelet deposition and the fall in platelet count was smaller in the plasmin experiments. C3d determinations revealed a slight activation of complement upon addition of plasmin, but the activation by xenoperfusion was much more pronounced and, at the end of the experiment, the C3d concentration was the same in the two groups.

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PubMed1986

Platelet aggregation is not essential for xenograft rejection.

Five rabbit kidneys were perfused at 80 mm Hg with heparinized human blood, five with platelet poor human blood, and five with human blood added prostacyclin. Time until blood flow decreased to 2 ml/min was significantly delayed by removal of platelets or addition of prostacyclin. Histological examination did not reveal any difference between the groups. It is concluded that platelets play an enhancing role, but they are not essential for xenograft rejection.

Animals↗
PubMed1986

On the role of platelets and leucocyte in renal xenoperfusion.

Five rabbit kidneys were perfused with heparinized human blood, five with platelet-rich, leucocyte-poor blood, five with platelet-poor, leucocyte-rich blood, and five with platelet-poor, leucocyte-poor, heparinized human blood. The kidneys were perfused at a constant pressure of 80 mm Hg and the time until the flow decreased to 2 ml/min was determined. Removal of platelets from the blood significantly delayed rejection. The effect of removing leucocytes was insignificant. Morphologically all groups revealed platelet aggregates, endothelial damage and ischemic changes of distal tubular epithelium.

Animals↗
PubMed1985

Xeno- and auto-perfusion of rabbit kidney. Machine perfusion with blood at 37 degrees C.

Five rabbit kidneys were perfused with human blood and another five with their own blood in a re-circulating oxygenated system at 37 degrees C. The flow decreased to 2 ml/min. within 30 min. in all xenoperfusions, while none of the autoperfused had decreased to this level by 60 min. Endothelial damage, exudation, and IgG deposits along the basement membrane of the glomerular capillaries were the discriminative features of the xenoperfusion. In these experiments, we were unable to demonstrate any major role of platelets in the process leading to decreased blood flow.

Animals↗
PubMed1984

Effect of cooling and warming rate on glycerolized rabbit kidneys.

Cooling and warming rates are known to be important determinants of viability for cryopreserved cells, but optimal rates have not previously been determined for any whole organ. In this study, rabbit kidneys, permeated with 2 M glycerol were cooled to -80 degrees C at four rates varying from 1 degrees C/hr to 3.1 degrees C/min and then rewarmed at four rates from 1 degrees C/hr to 4.2 degrees C/min, giving 16 experimental treatments. After gradual deglycerolization at 10 degrees C, each kidney was autografted and observed for 30 min. Assessment was by measurement of vascular resistance, immediate post-thaw lactate dehydrogenase (LDH) release, gross appearance, light- and electron microscopy, and tissue K+/Na+ ratio 30 min after transplantation. The best results were obtained after cooling at 1 degrees C/hr; warming rate had little apparent influence on the criteria used to assess function with the exception of LDH release, which indicated a preferred warming rate around 1 degrees C/min. Histological studies revealed extensive vascular damage, notably to the glomerular capillaries, that was minimized by very slow cooling. Freeze substitution, carried out on samples removed at -80 degrees C, demonstrated extensive ice formation in the interstitial space and, at the faster cooling rates, in the glomerular capillaries. Intracapillary ice formation was reduced in the kidneys cooled at 1 degrees C/hr.

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PubMed1983

The survival of pig to rabbit renal xenografts during inhibition of thromboxane synthesis.

Five rabbits treated with the thromboxane synthetase inhibitor Dazoxiben and five control rabbits received pig renal xenografts. Plasma albumin, complement factor C3, TXB2, 6-keto-PGF1 alpha, and serum TXB2 and 6-keto-PGF1 alpha were determined before and 1/2 hour after transplantation. The xenograft survival was significantly decreased in the Dazoxiben treated animals compared to the placebo treated animals determined as time to total cyanosis of the graft, total urine production, and time to stop of urine production. Lack of TXB2 production during blood coagulation confirmed inhibition of platelet thromboxane synthesis. The other determined variables showed no significant differences between the treated and the placebo animals.

6-Ketoprostaglandin F1 alpha↗
PubMed1968

Resistance changes in lipid bilayers: immunological applications.

The electrical resistance of a bimolecular lipid membrane in 0.1 molar NaCl decreases if antibody and complement are present on one side of the membrane and the homologous antigen is added to the other side. The reaction occurs within minutes and requires less than 0.1 microliter of antiserum.

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