Biomedical subjects
D J Potts
Publications and source records attributed to D J Potts.
Management of bleeding in early pregnancy in accident and emergency departments.
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Improved porcine renal preservation with a simple extracellular solution--PBS140.
In this prospective randomized trial a porcine model of renal autotransplantation was used to compare quality of preservation, as reflected by detailed analysis of posttransplant renal function, following 24-hr cold storage in phosphate-buffered sucrose (PBS140), hyperosmolar citrate (HOC), and University of Wisconsin (UW) preservation solutions. There were 6 deaths with primary nonfunction: 3 of 5 HOC, 2 of 5 UW, but only 1 of 5 PBS140. Analysis of the whole group and separate analysis of the survivors demonstrated significantly better renal function following preservation with PBS140 when compared with both HOC and UW, with a lower peak serum creatinine (P = 0.02) and improved loop of Henle function (P = 0.02). The animals in the PBS140 group also demonstrated a more rapid return to normal creatinine, higher GFR, improved tubular function, and higher effective renal plasma flow, with figures approaching statistical significance (P = 0.06-0.07). The proposal of UW as a universal storage medium prompted this study, and its results suggest the need for a clinical comparison of renal preservation using UW and PBS140 in a prospective randomized trial.
Cell swelling, co-transport activation and potassium conductance in isolated perfused rabbit kidney proximal tubules.
1. Isolated, perfused rabbit proximal tubules were used to study the effects of activation of the apical membrane sodium co-transporters, and of the effects of osmotically induced cell swelling, upon cell volume, basolateral membrane potential and apparent partial conductance of potassium. 2. Activation of electrogenic apical sodium co-transport caused a depolarization of the basolateral membrane and a reduction of the basolateral apparent potassium transference number. This was followed by a spontaneous partial recovery of potential and increase in apparent potassium transference number. 3. Stimulation of apical sodium co-transport led to a sustained increase in cell volume. 4. A sustained increase in cell volume (of similar magnitude to that seen after activation of apical membrane sodium co-transporters) was also caused by reduction of bath and perfusate osmolality by removal of 89 mmol l-1 mannitol from both lumen and bath solutions. 5. This reduction in bath and perfusate osmolality also led to a basolateral membrane hyperpolarization and an increase in basolateral apparent potassium transference number. 6. These observations support the possibility that some of the partial recovery of basolateral membrane potential (Vb1) during apical sodium co-transport stimulation is due to a cell volume sensitive change in basolateral potassium conductance.
Effect of phosphate-buffered sucrose flush solution upon the initial phase of ischaemic acute renal failure in the rat.
1. Experiments were performed upon anaesthetized rats to investigate the effect upon the initial 4 h of ischaemic acute renal failure of intrarenal flush with phosphate buffer (PB), sucrose alone and phosphate-buffered sucrose (PBS) solutions of differing compositions. 2. Kidneys flushed with PB immediately before 45 min pedicle clamp ischaemia exhibited a post-ischaemic function similar to that of control, non-flushed kidneys: they were isosthenuric and non-oliguric with a clearance of inulin (Cin) depressed to 10% of the pre-ischaemic value. 3. Kidneys flushed with 50 mmol/l sucrose in saline before ischaemia became isosthenuric, oliguric and had a more severely depressed post-ischaemic Cin compared with non-flushed kidneys. 4. Kidneys flushed with PBS containing either 50 (PBS50) or 140 (PBS140) mmol/l sucrose at pH 7 became polyuric after ischaemia, produced concentrated urine and had Cin values significantly higher than control kidneys. 5. Raising the pH of the PBS50 to 7.4 resulted in isosthenuric, polyuric kidneys that had a post-ischaemic Cin not significantly different from that of the control group. 6. It is concluded that the severity of the initial phase of ischaemic acute renal failure was significantly reduced by intrarenal flush with a PBS solution of pH 7; flush with PB or sucrose alone had no protective action.
Improved 72-hour renal preservation with phosphate-buffered sucrose.
The result of this study shows that a simple phosphate buffered sucrose solution (PBS) is better than hyperosmolar citrate (HOC) solution in the flush perfusion and hypothermic storage of canine kidneys for 72 hr prior to autotransplantation with immediate contralateral nephrectomy. The peroperative measurement of postreperfusion renal blood flow revealed a significant reduction after 60 min in kidneys preserved with HOC solution. All grafts and animals in the PBS group (5/5) survived with primary renal function compared with one in the HOC group (1/5), which functioned after a period of oliguria. The early serum creatinine and urea levels were significantly lower in the PBS group, with a return to normal range within two weeks. This is reflected in higher inulin clearances and a more rapid recovery of proximal tubular function in the PBS animals, which also demonstrated a more rapid return of loop function and the ability to concentrate urine.
Acetazolamide and transient responses of basolateral membrane potential of rabbit kidney proximal tubules perfused in vitro.
1. A study was made of the partial recovery of basolateral membrane potential that follows some depolarizing manoeuvres in cells of isolated perfused segments of rabbit proximal convoluted tubules. 2. Peritubular application of 10(-4) M-acetazolamide (a known inhibitor of the basolateral sodium-bicarbonate co-transporter) caused a hyperpolarization of both the basolateral membrane potential (Vbl) and the transepithelial potential (Vte). 3. Activation of electrogenic apical sodium co-transport caused a depolarization of the basolateral membrane followed by partial recovery of potential, and a sustained transepithelial hyperpolarization. The partial recovery of basolateral membrane potential was significantly smaller in the presence of 10(-4) M-acetazolamide applied to the peritubular fluid, although the magnitude of the initial depolarization was not significantly altered. 4. Addition to the bath of 0.5 mM-barium, a potassium conductance blocker, caused a transepithelial and basolateral membrane depolarization followed by partial recovery of potential. The partial recovery of basolateral membrane potential was significantly smaller in the presence of 10(-4) M-acetazolamide applied to the peritubular fluid, although the magnitude of the initial depolarization was again not significantly altered. 5. Increases in bath potassium concentration from 5 to 20 mM led to transepithelial and basolateral membrane depolarization followed by partial recovery of potentials. In paired experiments the partial recovery of basolateral potential was significantly reduced when 10(-4) M-acetazolamide was present in the bath. 6. These observations are consistent with the hypothesis that the basolateral sodium-bicarbonate co-transporter plays a role in the recovery of Vbl following these depolarizing manoeuvres.
Unilateral renal ischaemia in the rat: effect of contralateral nephrectomy and intrarenal flush with phosphate-buffered sucrose.
1. This study examined whether the severity of acute renal failure seen within 4 h of a 45 min period of unilateral occlusion of the renal pedicle could be reduced by removal of the contralateral healthy kidney and/or intrarenal flush with a phosphate-buffered sucrose (PBS50) solution. 2. After ischaemia, unflushed kidneys became oliguric and isosthenuric, with a fall in inulin clearance (Cin) to 0.1% of the pre-ischaemic value. Removal of the healthy contralateral kidney upon release of the occlusion caused no improvement in immediate post-ischaemic function. 3. Intrarenal flush with 1.5 ml of PBS50 resulted in a significantly improved post-ischaemic Cin, with increased urine flow rate and solute excretion; urine was also concentrated. 4. Protection of renal function against ischaemic damage was seen only when kidney tissue remained blood-free and exposed to PBS50 throughout the period of ischaemia, and when the speed of flush was similar to the expected renal blood flow (6 ml/min). Protection did not depend upon the presence or absence of the contralateral kidney. 5. The study also showed that functional removal of one kidney, either by pedicle occlusion or nephrectomy, caused an immediate rise in solution excretion from the contralateral kidney, but Cin remained unchanged. Unflushed severely damaged kidneys showed no compensatory response to unilateral nephrectomy, whereas kidneys flushed with PBS50 exhibited increases in solute excretion similar to those seen in healthy non-ischaemic kidneys.
A comparison of the relative effectiveness of three transplant preservation fluids upon the integrity and function of rabbit proximal convoluted tubules perfused in vitro.
Rabbits were anaesthetized and kidneys removed directly with no flush (group NF), or alternatively kidneys were flushed (group F) with sodium phosphate buffered 140 mmol/l sucrose (PBsuc 140), Collins C2 (C2) or Euro-Collins (EC) transplant preservation solutions and stored at 4 degrees C for 0-4, 24 or 48 h. Mid-cortical proximal convoluted tubule (PCT) segments were dissected from all groups and set up for microperfusion in vitro. Observations were made of tubule morphology, fluid reabsorption rate (Jv), bath leak of the glomerular marker iothalamate and transmural potential difference (p.d.), both at 37 degrees C and at 15-20 degrees C, in order to compare the relative effectiveness of the solutions in the preservation of tubule integrity and immediate function. Tubules from kidneys flushed with EC and C2 contained luminal debris and frequently had high bath leaks of iothalamate, both indicative of poor preservation of tubule integrity. In contrast, tubules from NF kidneys and PBsuc 140-flushed kidneys were free of luminal debris with a lower incidence of high iothalamate leaks. Tubules from PBsuc 140-flushed and EC-flushed kidneys after 0-4 and 24 h storage had Jv that were similar to those of NF kidneys. Tubules from all groups of flushed kidneys after 48 h cold storage and all tubules from C2-flushed kidneys showed reduced Jv values. In all cases Jv was reduced to approximately zero when the temperature was lowered to 15-20 degrees C. Transmural p.d. was similar in all groups except for particularly low p.d. values observed in tubules from C2-flushed kidneys after 48 h storage. These observations suggest that PBsuc 140 is more effective in the preservation of tubule function during prolonged cold storage than the glucose-based Collins solutions. The marked difference in the effectiveness of C2 and EC contraindicates the inclusion of magnesium (present in C2) for preservation of kidneys, as judged by experiments on the rabbit.
Application of cold flush preservation to in vitro microperfusion studies of kidney tubules.
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Increase in weight and water retention on overfeeding dogs.
Dogs, kept in metabolism cages, were weighed daily and the daily water intake, urine volume and evaporative loss of water measured or calculated. When the daily meal was doubled, the weight increased in two phases: during the first 4 d the increase in weight was more than could be accounted for by the deposition of protein, glycogen and fat so that water retention must have occurred; after the fourth day the increase in weight was slower and could have been due to the deposition of solids, without water retention. When carbohydrate was added to the meal either as starch or glucose, the increase in weight in the first 3 d was more than the weight of the added carbohydrate, showing water retention. After the third day the slower increase in weight could be explained by the deposition of solids. When the daily meal was supplemented with fat, increase in weight occurred uniformly throughout the period of overfeeding and was equal to or less than the added fat. There was thus no evidence for water retention. Addition of meat to the daily meal caused an increase in weight larger than the fat and protein of the extra meat. Meat therefore caused water retention. The results indicate that during overfeeding, deposition in the body of protein and glycogen, but not fat, determines water retention.
The effect of peritubular protein upon fluid reabsorption in rabbit proximal convoluted tubules perfused in vitro.
This paper describes an investigation of the effects of varying the peritubular protein concentration upon the rate of fluid reabsorption of proximal convoluted tubule segments of the rabbit kidney, isolated and perfused in vitro. Eleven moderately distended tubules, bathed with rabbit serum (60 g l.-1 protein) and perfused with an ultrafiltrate of serum (ca. 0 g l.-1) protein, reabsorbed fluid at a rate of 1.0 +/- 0.07 nl. mm-1 min-1. When the protein of the bathing solution was reduced by replacing the serum with ultrafiltrate there was little change in fluid reabsorption rate. A further eleven moderately distended tubules, bathed with physiological saline containing bovine serum albumin (60 g l.-1) and perfused with saline, reabsorbed fluid at 1.0 +/- 0.06 nl. mm-1 min-1. There was little change in fluid reabsorption when the protein concentration was reduced to either 20 or 0 g l.-1; these tubules responded to 10(-5) M-ouabain in the bath, or a temperature of 25 degrees C, by reducing their absorption rate to 0.13 +/- 0.05 nl. mm-1 min-1. Nine minimally distended tubules reabsorbed fluid at 0.8 nl. mm-1 min-1 when bathed with physiological saline containing bovine serum albumin (60 g l.-1) and perfused with saline. Under these circumstances reabsorption rate fell by 26% when protein was removed from the bath. A study of the pressure-diameter relationship was made for eight tubules typical of those used in this laboratory. The probable range of lumen hydrostatic pressures was discussed for the distended and undistended states. We conclude that the effect of peritubular protein concentration upon fluid reabsorption in proximal convoluted tubule segments perfused in vitro is dependent upon some property of the tubule wall that is changed when distension occurs.
How can I reassure my patient if I've never been in surgery?
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Microperfusion of isolated renal tubule segments in vitro in the rabbit [proceedings].
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Post-prandial drinking by dogs.
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The external water exchanges of normal laboratory dogs.
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Protective effects of lactobionate in modified phosphate-buffered sucrose.
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Comparison of the protective effects of phosphate-buffered sucrose and University of Wisconsin solution in a non-heart-beating liver donor experiment.
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